Troubleshooting Thermo Scientific DensityPRO Gauges

Transcription

1 Troubleshooting Thermo Scientific DensityPRO Gauges Key Words Current output board Communications Other troubleshooting Purpose A chapter in the user guide for the Thermo Scientific DensityPRO gauge is dedicated to troubleshooting. Providing the material from that chapter in this stand-alone document will enable users to keep troubleshooting procedures easily accessible. Note: This technical bulletin is to be used as a quick reference for troubleshooting the DensityPRO gauge. It is not meant to be used as a replacement for the installation and user guides. Note: Troubleshooting must be done only by qualified personnel. Note: Do not use the HART communication system for technical troubleshooting. You must use either the Thermo Scientific Model 9734 Handheld Terminal (HHT) or a computer with RS232/RS485 converter and the Thermo Scientific TMTComm communication software to access the technical troubleshooting capabilities of the DensityPRO system. The Current Output Board If you suspect a problem with the current output, first verify that wiring and jumper settings are correct for the current output configuration. The current output configuration is marked on a label on the inside of the gauge housing lid. There are three possible configurations: loop powered, non-isolated selfpowered, and isolated self-powered. Each configuration is discussed below. Loop powered: The default current output configuration is isolated, loop-powered. With this configuration, the 4-20 ma loop is supplied by the customer s programmable logic controller (PLC) or distributed control system (DCS). A jumper is placed across pins 4 and 5 of the J7 connector on the CPU board. J10-6 and J10-7 are for the 4-20 ma output connections. See Figure 1. The DensityPRO system is ESD sensitive. Use proper ESD protective equipment and procedures. Failure to comply with ESD procedures can result in circuit damage. Figure 1. Loop powered configuration Non-isolated self-powered: With the nonisolated self-powered configuration, power for the 4 20 ma loop is supplied by the gauge, but it is not isolated from the gauge circuitry. A jumper is placed across pins 3 and 4 of the J7 connector on the CPU board. J10-6 and J10-9 are for the 4 20 ma output connections. See Figure 2. This configuration should only be used if isolated configurations cannot be used.

2 Communication Problems If the gauge will not communicate at all, try hard booting the system. Figure 2. Non-isolated self-powered configuration Isolated self-powered: With the isolated selfpowered configuration, power for the 4 20 ma loop is supplied by the gauge, and the output is isolated from the gauge circuitry. The isolated piggyback board (p/n ) must be installed on the CPU. This puts the 4 20 ma output on connections J10-6 and J10-8. No jumpers are used for this configuration. See Figures 3 and 4. Note: This procedure will erase memory and return all parameters to the factory defaults. Remove power from the gauge prior to performing this procedure. 1. Locate the J11 connector on the CPU board. The blow-away jumper setting for normal operation is shown in Figure 5. Figure 3. Isolated self-powered configuration Figure 5. Blow-away jumper in normal operation position 2. With power removed, remove the blow-away jumper, rotate it 90 clockwise, and insert it onto the pins as shown in Figure 6. Figure 4. Isolated piggyback board If the current output is correctly configured and you still suspect a problem, attach an ammeter in series with the current output load and verify the current output at various levels. Use the commands from the User Service & Related Items submenu within the Security, Service, and Diagnostic Functions menu group to hold the current output at specific levels for testing. Figure 6. Blow-away jumper in erase memory position 3. Apply power to the gauge for approximately 30 seconds. 4. Remove power from the gauge, and return the jumper to its original position. 5. Apply power to the gauge. All parameters will be set to factory defaults.

3 Other Troubleshooting If the instrument is not functioning properly, review this section carefully and then follow the steps provided. Equipment Required 3. While the lid is removed, verify the red LED on the CPU board is lit (Figure 7). This indicates that the CPU is getting the 5 Vdc required for operation. For this procedure, you will need: One Model 9734 HHT or a PC with RS232/RS485 converter and the TMTComm software installed One multimeter Site Preparation You will need to access the gauge while it is in the housing and in the radiation field coming from the radioactive source on the opposite side of the pipe. The source shutter will need to be ON, and you will need to know whether the pipe is empty or full of process. If possible, fill the pipe with pure carrier. If you are in a classified area, a HOT WORK permit may be necessary. Procedure Figure 7. Location of CPU LED 4. If the LED is not lit, check the fuse. For AC powered systems, the fuse is a amp sloblow and is located on the AC power supply board (Figure 8). For DC powered systems, check the F1 fuse on the CPU board (Figure 9). If the gauge is powered by 120 Vac, this voltage will be present while accessing the gauge. Proceed with caution. Do not come in contact with this voltage. Figure 8. Location of fuse on AC power supply board 1. Verify the source shutter is in the ON position. If the source has an internal shutter, use a radiation survey meter to verify the shutter is working properly and that the source is on. Figure 9. Location of F1 fuse on CPU board 2. Remove the detector housing lid and connect the gauge detector to the Model 9734 HHT or to a PC that has the TMTComm software installed.

4 5. If the LED is not lit and the fuse is not blown, use a voltmeter to measure terminals 1 and 2 of the J12 connector (24 Vdc input) on the CPU (Figure 10). If Vdc is measured, the power supply is operating properly and supplying the correct power to the CPU. If the voltage is not there, the problem may be with the power supply or the supply voltage. If the sensor signal does not change or is zero when you cycle the source shutter or block the beam path, the detector signal is getting lost or corrupted somewhere between the scintillation crystal and the CPU. The problem may be related to the photomultiplier tube (PMT), the triangle board (p/n ), the cabling (p/n ), or the CPU (p/n ). 7. The next step is to turn on the diagnostic measurements feature. Use DAC Press the right arrow once to change the selection from Do not enable (Figure 12) to Do enable (Figure 13) to enable diagnostic measurements and then exit. Figure 10. Location of J12 connector (24 Vdc input) 6. Using DAC , bring up the Internal Value of Sensor Signal item. The value shown in Figure 11 is for example only. Internal value of sensor signal 2.057E4 Figure 11. Example internal value of sensor signal While the detector value is still displayed, close the shutter on the radioactive source or place something (other than a body part) in the beam path to attenuate some of the radiation getting to the detector. Do not place any part of your body, including your hands, into the radiation beam path. The displayed signal value should decrease in value. Open the source shutter or remove the object in the beam path. The signal value should increase and return to approximately the original value. Do not enable diag measurements Change to Do Figure 12. Diagnostics measurements disabled Do enable diag measurements Change to Do not Figure 13. Diagnostic measurements enabled With the diagnostic measurements turned on, the display will toggle between two screens (Figures 14 and 15). Five values are displayed. These values are explained in the next section..999 g/ml >9999 VD 2273 CTLSIG For setup, press Figure 14. Diagnostics measurement screen ERRSIG 6 CNT-ratio 1763 REF (cps) For setup, press Figure 15. Diagnostic measurement screen 2

5 Diagnostic Measurement Values In addition to the density reading, five values are displayed on the diagnostic measurement screens. ERRSIG: This value may also be shown as HVCorr, depending on the version of software in the instrument. ERRSIG is a relative value representing the length of the control pulses for high voltage control. This number should be at or near 0. If it is staying under 10, the detector is under normal control and working correctly. If this number is running from 10 to 50, the detector may be damaged (often from being exposed to temperatures over 140 F for some period of time), and its indication should be suspect. If this number is running from 50 to 256 (the highest possible value), the gauge cannot control the high voltage. It is likely that the detector has failed. CTLSIG: This value may also be shown as HVCtrl, depending on the version of software in the instrument. This is a relative value representing the amount of control time the CPU is using to control the detector. The value can be from 10 to The normal control range for a new detector is from 2000 to Every detector will have a different value, but the value should always be steady. If the value is ramping up or down, then the detector is faulty and not under control. REF(cps): This value is the REF count rate in cps. It should be 1/6 of the VD count rate. The CPU will adjust the CTLSIG until the VD gets to six times the REF count rate. If it is unable to reach this 6:1 ratio, the CTLSIG will ramp up to 8000, go back to 10, and ramp up again. If the REF(cps) is a low number like 5, the reference counts are getting lost somewhere between the PMT and the CPU. CNT-ratio: This value is the ratio of the DATA count rate (VD) and the REF(cps). The ratio should stay at 6:1, unless the R&D test items are enabled. In this case, the number will move from slightly below six to slight above six. This indicates that the CPU control is working properly. Recorded Values The values listed in Table 1 are useful to Thermo Fisher Scientific Technical Support when troubleshooting the DensityPRO system. Please have these values readily available when calling for assistance. To recall these values, press EXIT, enter the DAC, and press the down arrow. Record the value shown. Press EXIT again to return to the main screen. The first five values (ERRSIG through CNT-ratio) were accessed in step 7 of the above procedure. VD(cps): This value is the DATA count rate in counts per second (cps). It should be the same value as the internal value of the sensor signal (DAC ) recalled in step 1 of this procedure. If this value is above 9999, the display will show >9999. To display this value, you will need to enable the R&D test items by entering DAC The value will display in scientific notation. Be aware that other values will also change to scientific notation and lose their names. Therefore, it may not be desirable to leave this feature enabled very long. This value should increase with a lower density and decrease with a higher density.

6 Table 1. Recorded values for troubleshooting Parameter Name/DAC Description Value ERRSIG Error from stable control CTLSIG Control signal from CPU VD Data count rate in cps REF(cps) Reference count rate DNT-ratio VD/REF(cps) ratio Standardization value Snapshot of detector signal Density slope correction Pipe ID in inches Software version Time constant in seconds Carrier gravity in g/ml Solids gravity in g/ml Density of CAL point Density of CAL point CAL/STD ratio for CAL point CAL/STD ratio for CAL point Carrier attenuation coefficient Solids attenuation coefficient ma output value ma output value Source half-life value In addition to these offices, Thermo Fisher Scientific maintains a network of representative organizations throughout the world. Canada +1 (905) (905) fax China +86 (10) (10) fax India +91 (20) (20) fax United Kingdom +44 (0) (0) fax United States +1 (800) (713) (713) fax HART is a registered trademark of the HART Communication Foundation Thermo Fisher Scientific Inc. All rights reserved. Specifications, terms and pricing are subject to change. Not all products are available in all countries. Please consult your local sales representative for details.