rae systems

VRAE

MULTIPLE GAS MONITOR (PGM - 7800)

DIAGNOSTIC AND SERVICE MANUAL

(Document No: 017-4011-000) Rev. A.

RAE SYSTEMS INC. 1339 Moffet Park Drive Sunnyvale, CA 94089

January 2001

PGM-7800 Diagnostic & Service Procedure

1.0. Objective: This document provides detailed diagnostic and service procedures for service personnel in the factory and field service center. The procedure allows trained service personnel to perform a set of diagnostic tests to determine if the Unit Under Test (UUT) is functioning properly and performing within the specification. The procedure also helps to diagnose the possible causes of failures and suggest a number of corrective actions. A recommended service spares list is provided at the end of the manual. 1.1. Diagnostic and Service Requirements: In order to perform the PGM-7800 diagnostic and service procedures, the service person should be very familiar with the procedure described in the PGM-7800 Operation and Maintenance Manual (RAE Part Number: 017-4001). The following equipment is required:

PC with Microsoft Windows 3.1/95 (or later) operating system and serial port. Computer interface cable (RAE Part Number 008-3003) ProRAE Suite software (Diskettes) Flat head screw driver #2 Phillips screw driver Tweezers IC Puller (for removing electrochemical sensors) Multi-meter (0-10 Vdc, 0-150 mA, 0-10 Mega-Ohm)


Figure 1.1 Main components of VRAE


2.0. Trouble-shooting Guide: PGM-7800 problems can be grouped into 4 major areas: 1) Power supply - battery and charger 2) Sensors and measurement 3) Electronics 4) Programming The following trouble-shooting guide provides a quick reference for typical problems in each major area: 2.1. Power Supply - Battery and Charger Problem Possible Causes Test Procedures Can not turn on unit 1) battery charge is low

2) battery pack fuse is blown 3) connector pins bent or broken 4) membrane switch broken 5) defective electronics

1) Test 4.1 2) Test 4.1 3) Test 4.4 4) Test 3.2 5) Test 6.1

bAt message during operation

1) battery charge is low 2) defective battery voltage measurement circuit 3) excessive loading on the battery 4) defective battery

1) Test 4.1 2) Test 4.3 3) Test 4.2 4) Test 4.1

Unit runs less than specified duration:

1) excessive loading on the battery 2) memory effect of NiCd battery 3) old or defective NiMH battery pack 4) defective charger 5) incomplete charging


Battery is warm during normal operation

1) excessive loading on the battery 1) Test 4.2

Charger light does not turn on

1) alkaline battery is installed in PGM-7800 2) defective charger 3) bad LED

1) Test 4.1 2) Test 4.5 3) Test 6.2

Charger light does not change from red to green after overnight charging

1) defective charger 2) defective charging circuit 3) bad green LED 4) bad battery 5) ambient temperature too high or low


2) Sensor and Measurement: Problem Possible Causes Test Procedures Unit turns on, shows Configuration changed message

1) sensor added or removed 2) sensor is disconnected or loose from socket 3) defective sensor

1) Test 2.3 2) Test 2.3 3) Test 2.3

Sensor is installed but not showing on LCD

1) sensor is disconnected or loose from the socket 2) defective electronics 3) Sensor disabled

1) Test 2.3 2) Test 2.3 3) Test 4.5

No response or low response to gas input

1) sensor input is blocked or dirty filter 2) defective sensor module 3) defective electronics 4) weak, or leaking pump 5) sensor cover plate missing, loose, or misaligned 6) empty sensor position

1) Test 2.1 2) Test 2.4 3) Test 2.4 4) Test 2.2 5) Test 2.1 6) Test 2.1


Slow response to gas input

1) sensor input is blocked or dirty filter 2) defective sensor module 3) sensor has inherently slow response time 4) weak or leaking pump 5) sensor cover plate missing, loose, or mis-aligned 6) empty sensor position


Erratic reading

1) incorrect calibration 2) defective sensor module 3) defective electronics 4) weak or leaking pump

1).Test 2.5 2) Test 2.4 3) Test 2.4 4) Test 2.1

Non-zero background reading

1) dirty filter 2) incorrect zero calibration or zero drift 3) defective sensor module 4) non-zero background 5) carbon filter saturated or not installed


CAL Err message during calibration

1) incorrect calibration 2) previous calibration data is wrong due to sensor

change 3) defective sensor module or weak lamp 4) leak in flow path 5) defective electronics


Flashing CAL message during normal operation

1) excessive negative zero drift of sensor

1) Test 2.5

Reading stuck at a fixed value when exposed to high concentration of gas

1) incorrect span calibration 2) defective sensor module 3) leak in flow path

1) Test 2.5 2) Test 2.4 3) Test 2.1

During normal operation, pump message flashing

1) Gas inlet blocked or no connection to inlet port 2) weak or inoperative pump 3) pump stall threshold needs adjustment

1) Test 2.1 2) Test 2.2 3) Test 2.7

xxx installed bias error message on LCD

1) bias switch in wrong position for Toxic1 sensor 2) defective sensor module

1) Test 2.8 2) Test 2.4

2.3. Electronics Problem Possible Causes Test Procedures LED, back light, buzzer or vibrator alarm inoperative

1) defective component 1) Test 6.2

Missing segment on the LCD

1) defective LCD 2) temperature too low 3) contrast set too low

1) Test 6.3 2) Test 6.3 3) Test 6.3

Random characters on the LCD

1) CPU hang-up 2) defective electronics 3) wrong firmware or error in firmware 4) bad LCD 5) temperature too high or low 6) contrast too high or too low


No response to key press or can not turn off unit

1) membrane disconnected from PCB 2) defective membrane keys 3) CPU hang-up

1) Test 6.8 2) Test 3.2.26 3) Test 6.5

Back light does not turn on in low ambient light

1) defective electronics or component 2) back light threshold needs adjustment

1) Test 6.2 2) Test 6.2

2.4. Programming


Problem Possible Causes Test Procedures Unable to put into programming mode

1) unit in display mode 2) configured for password protection

1) Test 7.2 2) Test 7.3

Lost password 1) unit configured for password access 1) Test 7.3 Unable to configure port message from ProRAE Suite software

1) port not available in this PC 1) Test 7.5

NAK message from ProRAE Suite program

1) Cable or connection problem 2) port configuration problem 3) PC hardware or operating system problem

1) Test 7.5 2) Test 7.5 3) Test 7.5

Time out message from ProRAE Suite software

1) unit not in Ready mode 2) cable or connection problem 3) PC hardware or operating system problem

1) Test 7.5 2) Test 7.5 3) Test 7.5

Calibrates OK, but VOC readings off by constant percentage.

1) Wrong calibration or measurement gas selection 1) Test 5.2

Unit beeps once every minute or so.

1) comfort beep option turned on

1) Test 7.6

3.0. Diagnostic Modes: 3.1. Keypad Diagnostic Mode 3.1.1. All RAE Systems gas monitors have a Diagnostic Mode for evaluating the condition of sensors, lamps, pumps, batteries, etc. This is distinct from the usual diagnostic tests the instrument performs automatically during routine start-up. All the usual functions can be performed in diagnostic mode, such as calibration and monitor set-up. In diagnostic mode all sensor outputs (and most other measured values) are displayed as raw values (a/d counts) without corrections or conversion to standard units. The following diagnostic procedures will make use of this mode when appropriate. Whenever the procedures state place the unit in diagnostic mode, use the following steps to turn on the unit in this special mode. 3.1.2. Entering Keypad Diagnostic Mode: With the unit turned off, hold down the [Y/+] key. While still holding this key down, depress and hold the [MODE] key. Hold both keys down for 2 seconds, then release both keys. The VRAE will display ON!... followed by the software version number, then the Diagnostic Mode message. The unit will then go through the normal start-up tests. Once the monitor is ready, the display will show raw values for each installed sensor, with the word RAW in the center of the bottom line of the display. 3.1.3. In Keypad Diagnostic Mode, use [N/-] and [MODE] together; just as in normal mode, to enter the Programming Menu. CAUTION: When calibrating in Keypad Diagnostic Mode the system does not check for a difference between the span and zero calibration points. This can be useful if calibrating at a low level. The user must manually verify, from the raw values in air and with calibration gas applied, that the sensors are working correctly. The instrument will also not save the calibration date. 3.1.4. Use the [MODE] key alone to step through the special diagnostic screens in the following sequence:

Keypad Diagnostic Screens Raw Sensor Values

Sensor Names


Battery Type (Alkaline/NiMH/NiCD)

LCD contrast adjustment

LEL sensor type

Clock/Voltage/Temperature

Sensor expiration dates

Pump current/Stall setting (adjustable)

Ambient light sensor output/Threshold (adjustable)

S/N and Pump speed

Battery deep discharge

Battery duration

Communicate with PC

3.1.5. Raw readings: 3.1.6. Verify that there are no flow obstructions, and that the pump is operating correctly. Table 3.1 has the normal 10A raw values for the sensor in air (fresh air value) and with the standard calibration gas applied (span value). The most important indicator of sensor operation is the delta value, which is the difference between the span output and the zero output.

Sensor Type

Calibration Gas RAW Zero range RAW Span range Span Range

LEL 50% LEL Methane 1800-2600 2200-3100 >400 %VOL/LEL 2.5% VOL Methane 1800-2600 1840-2700 >40-100 %VOL/LEL 20% VOL Methane 1800-2600 2100-2900 >300 O2 (Alpha) 99.9% Nitrogen 950-1250(Fresh Air) 100-300(N2) >650* O2 (City) 99.9% Nitrogen 2100-2300(Fresh Air) 100-300(N2) >2000*

CO 50 ppm CO 100-300 300-800 >200 H2S 25 ppm H2S 100-300 450-1300 >500 SO2 5 ppm SO2 100-300 550-1000 >450 NO 25 ppm NO 100-300 250-550 >150 NO2 5 ppm NO2 100-300 250-850 >150 Cl2 10 ppm Cl2 100-300 350-1500 >250 NH3 50 ppm NH3 350-820 1350-3500 >1000 HCN 10ppm HCN 100-300 150-500 >50 PH3 5ppm PH3 100-300 150-500 >50

Table 3.1 VRAE RAW values

3.1.7. Note the raw fresh air output of the sensor. Apply the span gas and wait until the reading is stable to within a few counts. Note the raw span output of the sensor. Calculate the delta (span fresh air).


3.1.8. Fresh air values significantly below the values in the chart could be due to an electronic problem in the analog circuit. Fresh air values significantly higher than the values in the chart generally indicate a shorted or dirty sensor. 3.1.9. The delta is the most significant indicator of sensor/lamp condition. Fresh air values slightly below the chart values are acceptable if the delta is above the minimum value. A low delta means that the sensor is not responding to the test gas, which is usually caused by a weak sensor or a leak in the flow path. LEL sensors that respond to span gas by going down indicate a poisoned sensor. 3.1.10 Sensor Name All the toxic, oxygen and LEL sensors have a non-volatile memory which contains the sensor identification and other vital information, such as manufacturing date, expected operating life, etc. If a sensor is programmed and installed properly in the monitor, the sensor name should be displayed. If the sensor name does not show up in the display, then the sensor may not be programmed properly or may be defective.

3.1.11. Battery Type and Battery Temperature A rechargeable NiMH, NiCd battery pack or an alkaline battery adapter can power the VRAE monitor. The microprocessor automatically detects the type of battery installed inside the monitor and displays the type of battery. The rechargeable battery includes a temperature sensor. The temperature sensor reading is also displayed. 3.1.12. Display LEL or VOL Raw Reading This display shows the present raw reading of the LEL or a combination of LEL/VOL sensor. The top display shows the mode of the combustible sensor. The bottom line shows the instantaneous reading of raw counts from the LEL or VOL sensor. By pressing [N/-] key the sensor mode can be switched from %LEL to %VOL and vice versa. If a standard LEL sensor is installed, press [N/-] key will toggle on and off the LEL sensor. 3.1.13. Sensor Expiration Date This display shows the expiration date (month and year) of all the installed sensors in the VRAE monitor. The expiration date is calculated based on the manufacturing date and expected life of each sensor, which were stored inside each sensor when it was fabricated in the factory. If the current date exceeds the expiration date of any sensor, the performance of the given sensor can no longer be guaranteed. It is strongly recommended that the user replace the sensor immediately to ensure proper operation of the sensor. 3.1.14. Adjust Pump Stall Threshold This display can be used to calibrate the pump stall threshold. If the gas inlet is blocked but the pump does not shut down, or the pump shut down too easily with a slight blockage to the gas inlet, then the pump stall threshold value may be set too high or too low. Use the following steps to adjust the pump stall threshold. 1. The maximum and average pump current is displayed on the first row: Pump = xxx/zzz. The current

pump stall value is displayed on the second row: Stall = yyy +/-. The typical maximum and average pump current without any blockage should be between 810. The typical stall value should be higher than the un-blocked pump current by at least 8-10 counts.

2. The user can block the gas inlet and watch the pump current reading. If the pump current reading does not increase significantly (i.e. more than 35 counts), then there may be a leak in the gas inlet or the pump is weak or defective.


3. Use [Y/+] or [N/-] key to increase or decrease the stall value until it is about 8-10 counts above the un-blocked pump current reading. Press [MODE] key to exit this display. If the threshold value is changed, a message Save new stall threshold? will appear. Press [Y/+] to confirm the change, [N/-] or [MODE] key to abandon the changes. 3.1.15. Adjust Back Light Threshold This display can be used to calibrate the LCD back light turn on and off threshold. Use the following steps to adjust the back light threshold. 1. The present ambient light level is displayed on the first row: Light = xxx. The current back light

threshold value is displayed on the second row: Trigger = yyy +/-. In a brightly-lit room, the light reading should be above 120.

2. The user can block the light sensor, which is located at the upper left corner of the monitor, with a finger and watch the light sensor reading. The light reading should drop to less than 100. Determine the ambient light level when the back light should be turned on and record the light sensor reading.

3. Use [Y/+] or [N/-] key to increase or decrease the trigger value until it is about the same as the previously recorded light sensor reading. Press [MODE] key to exit this display. If the threshold value is changed, a message Save new light threshold? will appear. Press [Y/+] to confirm the change, [N/-] or [MODE] key to abandon the changes. 3.1.16. Serial Number and Pump Toggle This display shows the unit serial number. If a pump is installed and pump speed control circuit available, the display Pump=Low/(High) may be toggled by pressing the [N/-] key. Note that changes made here are only for testing the pump condition and do not become saved in the nonvolatile memory. See section 4.7 to update the pump speed setting. 3.1.17. Start Battery Deep Discharge This display can be used to begin a battery deep discharge cycle. Certain rechargeable batteries may require deep discharge before charging again. To start the deep discharge: First connect the charger and select [Y/+] key to enter the deep discharge mode and answer with [Y/+] key when asked to confirm. The unit will turn off charger current and draw its maximum current until the battery voltage reaches 4.0 volts. With the charger connected, a charge cycle will then begin. 3.1.18. Display Battery Duration Time This display shows the run time of the last time the unit powered itself off due to a low battery or turned off by the user. It is useful for battery life testing.

4.0. Diagnostic and Service Test Procedures:


4.1. Power supply / Battery / Charger

Figure 4.1 VRAE Battery

Figure 4.2 VRAE Battery Pack

FUSE

V1V2


4.1.0. Battery Voltage Test: 4.1.1. Turn off the power to the VRAE. Open the battery cover by removing the 2 Philips head screws from the backside (see Figure 1). 4.1.2. Remove the rechargeable battery pack or alkaline battery adapter from the unit. 4.1.3. Visually inspect the pogo pins on the monitor and the contact surfaces on the battery pack or adapter. Broken or bent pins, or pins that do not push in and out, should be replaced. If the battery contacts are soiled or tarnished they can be cleaned with a mild solvent, such as methanol, or a soft eraser or other non-abrasive tool. 4.1.4. Use a voltmeter to measure the voltage V1 and V2 (figure 4.1). For rechargeable batteries, V1 should equal V2. The alkaline battery adapter will have no voltage at V1. Be careful to avoid shorting the contacts as this could blow the internal fuse (3/8 amp). If the voltage is less than 4.2V the unit will not turn on. If using alkaline (AAA) cells, replace them with fresh cells when the voltage is less than 4.4V. If using rechargeable batteries, the batteries must be charged when the voltage is below 4.4V. After replacing or recharging the batteries, check the voltage again. Fresh alkaline batteries should read over 6V. Fully charged NMH batteries should read over 4.8V. 4.1.5. If V1 or V2 reads 0, then the internal fuse is blown. Replace the battery pack or adapter. 4.2. Battery loading 4.2.1 Remove the battery from the unit. Set the DC power supply to 4.8V DC. Connect the negative output to the negative pin on the back of the VRAE. Connect the positive power supply output to the positive side of a current meter. Connect the negative side of the current meter to the positive pin on the back of the VRAE (see figures 4.2 and 4.3).

Figure 4.3 4.2.2. Current should be about 0.3 to 0.5 mA with the unit off. Turn on the unit in Serial Port Diagnostic Mode. Use the functions to turn the pump and lamp on and off. The nominal current for each component is:

To VRAE battery contact pins

-

+

-

+ - DC POWER SUPPLY

DC CURRENT METER

+


Basic unit: 17 - 19 mA Pump current: 15 17 mA with motor drive = 250 4.2.3. If the current exceeds the limits in the table above, then follow troubleshooting procedures for that section of the instrument. 4.3. Battery voltage Measurement Circuit 4.3.1. Follow the steps in 4.2.1 (the current meter is not necessary). 4.3.2. Turn on the power supply. Turn on the VRAE. Press [MODE] 2 times to get to the battery voltage display. The display should read 4.8V 4.3.3. Increase the voltage to 6V. The display should read 6V. 4.3.4. Slowly decrease the power supply voltage. At 4.4V the display should begin flashing Bat. At 4.2V the unit should turn off. 4.3.5. If any of these tests fail, the unit should be returned to the factory for repairs. 4.4. Battery Condition Tests 4.4.1. Charge the batteries for 8 hours or until the green charge indicator lights. 4.4.2. Measure the voltage across the positive and negative contacts of the battery (test procedure 4.1). If the voltage is


4.5. AC Adapter Output Test 4.5.1. Plug the 12VDC adapter into an appropriate AC source. Measure the voltage at the DC connector. The inside contact is positive. If the output is not at least 12V, then the adapter is defective and must be replaced. 4.5.2. Inspect the DC connector. Make sure that the pin is at least 11 mm long and is not corroded or otherwise contaminated. Plug the AC adapter into the VRAE and into an AC outlet. With the battery removed from the unit, measure the voltage between the + and pins in figure 4.3. If the measured voltage is less than 10 VDC, then there is a loose or broken wire or a poor contact. Trace the circuit from the external connector to the PC board to the battery connector to determine the cause. 4.6. Battery Charging 4.6.1. Remove the battery cover from the VRAE. Make sure there is a NiMH battery pack in the unit. The unit will not charge or operate from the AC adapter if the alkaline battery adapter is installed. 4.6.2. Perform the Battery Condition Test (Section 1.5), using the VRAE to charge the batteries. If the batteries fail, perform the AC Adapter Output Test (section 1.6.2). If the adapter output is less than 12V, then replace the adapter. If the adapter output is good, then replace the battery pack. 4.6.3. Battery Replacement Replacing and Recharging Battery Pack 1. Turn off power of the VRAE. 2. Refer to Figure 7.1, unscrew two case screws from the bottom of the monitor case and remove the battery

cover. 3. Remove the battery pack from the battery compartment. 4. Place a new battery pack in the battery compartment. Make sure that the contacts on the battery pack

matches with the battery pins inside the compartment.

5. Close the battery cover and tighten the screws.

Replacing Alkaline Battery Adapter 1. Insert four fresh AA size alkaline batteries into the alkaline battery adapter. Make sure that the polarity

of the battery is correct. 2. Follow the same procedure as described above to replace the battery adapter. Note: the internal charging circuit is designed to prevent charging to alkaline batteries when alkaline batteries are installed inside the monitor. 4.7. Ambient Temperature


4.7.1. If the room temperature is >40 C the batteries may not charge properly. 4.7.2. If the temperature is colder than 10C the batteries will not be charged to full capacity.

5.1. Pump and Flow Related Problems 5.1.1. Remove the sensor adapter to the VRAE. Check for obstructions or leaks. Check the condition of the o-ring or filter seal. Make sure the sintered metal filter is oriented properly. 5.1.2. Check the tubing between the inlet port and the pump for kinks, obstructions, or leaks. Check that the pump outlet port is not loose, broken, kinked, or leaking. 5.1.3. With the pump on, connect a flow meter to the VRAE inlet connector. The minimum acceptable flow rate is 500 ml/min. If the flow is too low check for obstructions and leaks as in section 2.1. 5.1.4. If there are no obstructions or leaks, and the flow rate is still low, check pumps current from the Keypad Diagnostic mode. If the unblocked current is correct but does not increase when the inlet is blocked, then the pump should be rebuilt or replaced (P/N 300-0012-060). Replacement valves and diaphragms are available through RAE Systems (P/N 081-0006-000). 5.1.6. To distinguish between a bad pump and a bad pump drive circuit, use the diagnostic modes. A bad pump will have raw counts out of limit. Test the drive circuit by changing the MDRV parameter. The pump speed should change as this parameter is changed (default value is 250) 5.2. Sensor Response Tests 5.2.1. Calibration 5.2.2. Inaccurate or improper calibrations can cause erratic readings, especially if the unit is calibrated with a gas to which the unit has a low sensitivity or with a standard gas at a very low concentration. In normal operating mode the software checks for a minimal difference in sensor output between span and zero calibration data. This check is skipped if the calibration is performed from Keypad Diagnostic Mode. 5.2.3. To check the system response to calibration gas, use the raw output values in the Key Pad Diagnostic Mode (section 4). Apply the calibration gas and observe that the sensor responds sufficiently. 5.2.4. If the sensor is responding well to the chosen calibration gas, allow the unit to warm up for at least 15 minutes, still in the Diagnostic Mode. If the sensor zero continues to drift, then the sensor must be serviced. 5.2.5. If the sensor zero point is stabile, then, while still in Diagnostic Mode, and proceed to the calibration menu (hold down [N] and [MODE]. Perform a fresh air calibration followed by a span gas calibration. 5.2.6. If calibration fails despite a good response to gas, then there is an electronic problem and the unit should be returned to the factory for service.


5.2.7. If calibration is successful, then turn off the unit and restart it in normal mode. Apply the test gas and observe if the unit is reading correctly. If it is not then it must be returned to the factory. 5.3. Non-zero Background 5.3.1. Fresh air or zero calibration should be done in an area known to be free of gases that would affect the sensors. Zeroing in the presence of such gasses will result in inaccurate readings, especially at low concentrations. 5.3.2. If you are unsure of the purity of the air, or if you are seeing non-zero background readings after a good calibration, then use a bottle of zero air during the fresh air calibration. This is the only way to be positively differentiated between a faulty sensor and a real background signal. If you obtain a good calibration with zero air, and then re-check the zero with the same bottle of zero air, then you can have confidence that the instrument is working properly and the background signal you are seeing is caused by something in the environment. 5.3.3. If, after a zero air calibration, you do not obtain a stable zero when applying the zero air to the instrument, then the sensor does not have a stable zero point and must be serviced.

5.3.4. Sensor Replacement: The toxic, combustible and oxygen sensors all have an expected operating life. Under normal operating condition, most sensors will lose its original sensitivity after the expected operating life and needs to be replaced. Each sensor module in VRAE includes a non-volatile memory that records the manufacturing date of the sensor. In the diagnostic mode, the microprocessor will check the date code and display the expiration date of each sensor. The user should replace the sensor when the current date exceeds the expiration date of a sensor.

Note: see also - TN-151 on Sensor Replacement & Maintenance - TN-114 on Sensor Specifications & Cross-Sensitivities - TN-144 on LEL sensor Poisoning - TN-156 on LEL sensor Correction Factors - TN-153 on TC sensor Applications - TN-152 on O2 sensor Operation - TN-155 on O2 sensor (Alpha) Installation Sensor Replacement Procedure The oxygen and combustible sensor each has its unique sensor sockets in the VRAE monitor. The three toxic sensor sockets in the VRAE monitor allow the users to plug in any three sensors selected from the series of toxic sensors offered by RAE Systems Inc. 1. Turn off power of the VRAE. 2. Refer to Figure 7.1, open the battery cover by unscrew the two screws from the bottom of the monitor

case. Remove the battery pack. 3. Open the bottom cover of the monitor case by removing the 6 screws that holds the bottom case.


4. Refer to Figure 7.1, carefully unscrew four No. 2 screws that hold down the gas piping cover to the PCB and sensors. Remove the gas piping plate.

5. Refer to Figure 7.1, identify the location of a specific sensor and remove the sensor by gently pulling the

sensor upward. 6. Plug a new sensor into the empty sensor socket. Make sure that black line on the sensor label is lined up

with the white marker on the PCB and the sensor pins are aligned with the socket before pushing down the sensor.

7. Replace the gas piping cover and tighten the four screws to hold down the sensors. Replace the battery

pack and the monitor cover. 8. Turn on the power of the VRAE. The microprocessor will automatically recognize the sensors installed

and configure the monitor accordingly. 5.3.5. Special Bias Voltage for Toxic Sensors: The NO and NH3 toxic sensors require a special 300 mV bias voltage to operate. There is a dipswitch located on the PCB next to the sensors. When NO or NH3 toxic sensor is plugged into the toxic sensor socket, it is necessary to turn the dipswitch for the corresponding sensor to ON position to enable the bias voltage. It is very important to set the bias switch to the correct position when installing the toxic sensors. 5.3.6. Sensor missing or not identified 5.3.6.1. The VRAE sensors have sensor type and expiration date stored internally. During the power-on tests the unit identifies all installed sensors and compares this to the configuration list. If the two do not match the Configuration changed message appears. If sensors have been added or removed, then the unit will store the new configuration and no additional action is necessary. 5.3.6.2. Verify the sensor configuration: Make a note of which sensors the unit does identify by pressing [MODE] once from the instantaneous display. Turn off the unit. Remove the top cover. Disconnect the battery. Failure to disconnect the battery before removing or installing sensors could blow the battery pack internal fuse. Remove the gas piping plate. Verify the identity of each installed sensor. Remove, inspect, and re-insert each sensor making sure each is fully seated in its socket. The tops of the sensors should all be at nearly the same height. Pay particular attention to any sensors that were not identified. If pins are missing or the sensor or circuit board shows signs of damage do not re-insert the sensor: it must be replaced. 5.3.6.3. Re-connect the battery and turn on power. Configuration changed may appear now even if all the sensors are working. Note which sensors are identified. If all the installed sensors are now identified, then turn off power and re-assemble the unit. A full calibration must be performed before using the unit, as calibration data may have been lost. Sensors which require a bias (NO and NH3) must be installed, with a charged battery connected, for 24 hours before stable readings can be obtained.


5.3.6.4 If the sensor configuration is still not correct, then either the sensor is bad or there is an electronic problem. If possible, try replacing the sensor that is not recognized with a known good sensor to determine if the problem is with the sensor or the unit. Note that if NONE of the sensors can be identified; try removing sensors one at a time. A bad memory chip on one sensor may prevent the monitor from reading any of the sensors IDs. If this fails to isolate the problem, then the problem is with the boards in the unit. 5.4. Pump Stall Adjustment. 5.4.1. The Pump alarm can occur if the pump current exceeds the stall threshold value or if the pump current is 0. The pump current may increase over the threshold value as the pump ages or if the diaphragm is stiff due to cold temperatures. Pump current may also increase if the inlet is blocked or if drawing the sample through a long length of tubing. Before adjusting the pump stall threshold, make sure the flow path is not obstructed. 5.4.2. Turn on the unit in Key Pad Diagnostic Mode (Section IV). The pump alarm is disabled in Diagnostic Mode. Press the [MODE] key 8 times to get to the Pump = screen. The pump turns on and the display indicates the current that the pump is drawing. The underneath this value is the stall value. Pump currents above this level will cause a pump stall alarm in normal mode. 5.4.3. If the pump current is 0 then check for loose or broken wires. If the wires are intact, check the voltage between the red and black wires. It should be 3.5V. If the voltage is correct, then replace the pump assembly. If the voltage is not correct, then replace the analog PC board. 5.4.4. If the pump is operating, block the inlet with your finger and observe the change in pump current:

No change or only a few counts:

1) Pump current < stall current means there is a leak in the flow path between your finger and the pump intake. Check the probe, the internal tubing, the gas plate, the pump inlet nipple, and the pump diaphragm.

2) Pump current > stall current means that the inlet is blocked. Check the probe, the sintered metal filter, and the internal tubing for obstructions.

Changes, but pump current still < stall current

Check for leaks. If none are found, then reduce the stall threshold to be less than the current with the inlet blocked. Use the [N/-] key to reduce the stall limit.

Changes, but pump current > stall current even with inlet unblocked

Check for obstructions. If none are found, then raise the stall threshold. Use the [Y/+] key to raise the stall value to a point midway between the open and blocked values.

5.4.5. If the pump current exceeds 50 counts with no obstructions, then the pump assembly should be

replaced.


5.4.6. Sampling Pump Replacement The sampling pump is positive displacement piston pump. When approaching the end of the specified lifetime of the pump, it will consume higher amount of energy and reduce its sample draw capability significantly. When this occurs, it is necessary to replace the pump. 1. Turn off power of VRAE gas monitor. 2. Refer to Figure 1.1, open the monitor cover, remove the battery pack, carefully unscrew four No. 2

screws that hold down the gas piping plate to the PCB and sensors. Remove the gas piping plate. 3. Pulls loose the connector of the pump wire. Unscrew the two screws that hold the pump assembly to the

PCB. Disconnect the Tygon tubing that connects the pump to the gas inlet port. 4. Replace a new pump assembly. Connect the Tygon tubing to the gas inlet port. Connect the pump wire

and screw down the pump assembly to the analog PCB. 5. Refer to Figure. 1.1, replace the gas piping plate and tighten the four screws to hold down the sensors.

Re-place the battery pack. Replace the battery cover.

PROGRAMMING MODE Press [N] and [MODE] together for 3 seconds to enter [Mode] to return

Calibrate Monitor? (Press[Y] to select menu) Fresh Air Calibration? Y

N


Multiple Sensor Calibration? Single Sensor Calibration? Modify Span Gas Value ? Change LEL Span Gas ?

Change Alarm Limits? Change High Alarm limit? Change Low Alarm limit? Change STEL alarm limit? Change Average alarm limit?

View or Change Datalog? Reset Peak and Minimum? Clear All Data? Change Datalog Period? Select Data Type? View Datalog? Enable/Disable Datalog?

Change Monitor Setup ? Change Site ID? Change User ID? Change Alarm Mode? Change User Mode? Change Real Time Clock? Change Backlight Mode? Change Password? Change Pump Speed? Change Averaging Method?

Change Sensor Configuration? Change LEL /VOL Sensor Type? Enable / Disable Sensor? Change Dilution Ratio? Change LEL Gas Selection?

N

Mod

Mode

Y

N

Y

Mode

N

Mode

Y

N

N Y

Mod

N

N

N

N


Serv i ce Par t s f or V-RAE PGM-7800

Part Number Description Price (ea.)

002-3013-000 Wrist strap $ 15.00012-3051-000 NiMH battery pack, PGM-7600/7800 $ 155.00012-3052-000 Alkaline battery adapter $ 35.00012-3016-000 Battery cover, PGM-7200/7600/2000/7800 $ 10.00017-1100-005 PCB,PGM-7800/7840 VRAE $ 150.00017-1101-005 PCB,PGM-7800,LCD,Rev.E $ 75.00017-2010-000 Gas Piping Adapter, PGM-7800 $ 10.00017-2011-000 Sensor Adapter, PGM-7800/7600 $ 10.00017-2104-001 Membrane Panel, PGM-7800 VRAE $ 40.00017-3013-000 Sub-Assembly, PGM-7600/7800, Sensor Adapter $ 25.00017-3015-000 Sub-Assembly, 7800/7600, Probe With Adapter $ 35.00017-3016-000 Assembly, PGM-7800, Battery Cover $ 10.00017-3017-000 Assembly, PGM-7800, Housing Top $ 20.00017-3018-000 Assembly, PGM-7800,Housing Bottom $ 20.00017-3035-000 Assembly, PGM-7800,Gas Plate $ 42.00081-0006-000 Pump rebuild kit, PG-7500/7600/75/76 $ 40.00300-0012-060 Pump Assembly, PGM-7200/7600 $ 295.00310-0006-000 LCD, Standish, PGM-30/72007600 $ 75.00411-0005-000 Tubing, Teflon, AWG#9 (for probe) (per foot) $ 5.00430-0001-005 Screw, battery compartment, 4-40, (pack of 5) $ 5.00430-0005-005 Screw, 6-32, 1 (pack of 5) $ 5.00430-0074-005 Washer, screw retaining, Nylon (pack of 5) $ 5.00430-0081-005 Screw, 4-40, 5/8 (pack of 5) $ 5.00500-0036-000 Battery charger, 12V 500mA, 110V $ 35.00500-0036-001 Battery charger, 12V 500mA, 230V $ 35.00

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