"MICRO SWITCH" (125PC05D1)Pressure Sensor Replace.Help Needed - Page 1
Forum section: electronics / repair

author: daisizhou
author_rank: Super Contributor
timestamp: May 15, 2025, 12:34:02 am
content: I disassembled the pressure sensor from the PCB.The sensor housing has the "MICRO SWITCH USA" mark.And there is a hand-engraved "H11155" "J1238"mark.It was produced in 1989.Model is 125PC05D1.Please see the attached picture for the data sheet.There are 4 terminals at the bottom,I used the resistance meter to measure the resistance values,1-2(3.46K) 1-3(5.20K) 1-4(3.47K)2-3(3.37K) 2-4(3.29K) 3-4(3.38K)I used 4 4K resistors,Simulating a bridge resistor network,Connect to the PCB circuit board pressure sensor position,Display Normal.It was found that the pressure sensor had a thermal stability failure.Zero drift[The pressure sensor (S+, S-) voltage shifted from 0.15mv to 0.33mv].I can't find any replacement for it, if you know please let me know, thanks

author: daisizhou
author_rank: Super Contributor
timestamp: May 15, 2025, 06:56:12 am
content: The sensor comes from the RT-200 flow moduleRT-200 manual(https://mega.nz/file/sMYVDYCS#Uezoi3J0ui5RHs7EFoCrBJ3jXdoJ0x2UB1VggLn92Lw)Fault manifestation:After normal startup, "HELP 0" is displayed,Press "30" to see the "V/F" display value drop to 33 and continue to decrease.When "V/F" is within the range of (250-500), press the "zero" button to return to zero,But when the value is lower than 250, it is limited to "HELP 0" and cannot be reset to zero.Here is the video of my test

author: Poroit
author_rank: Frequent Contributor
timestamp: May 15, 2025, 08:36:08 am
content: G'day daisizhou,This Differential Pressure Sensor is on the Flow PCB....is that correct?Do you have Section 7.0 of the manual?Have you measured a Supply Voltage on any of the four pins?Have you had a look at Honeywellhttps://automation.honeywell.com/au/en/products/sensing-solutions/sensors/pressure-sensorsfor a replacement?https://www.te.com/en/products/sensors/pressure-sensors/board-mount-pressure-sensors.html?tab=pgp-storyhttps://www.analog-micro.com/en/products/pressure-sensors/board-mount-pressure-sensors/https://au.rs-online.com/web/p/pressure-sensor-ics/1331912

author: daisizhou
author_rank: Super Contributor
timestamp: May 15, 2025, 09:45:29 am
content: Quote from: Poroit on May 15, 2025, 08:36:08 amYes.It is on the flow circuit board.It looks like it forms a differential amplification signal voltage output (Hi, Lo) with LM346N, LM307, OP11...Sorry, the PDF file above is not clear, I uploaded a clear full versionhttps://mega.nz/file/sMYVDYCS#Uezoi3J0ui5RHs7EFoCrBJ3jXdoJ0x2UB1VggLn92LwI have not tested the voltage of the 4 pins of the pressure sensor,I measured the input voltage connected to the pressure sensor PCB, the supply voltage is +14.5v, -14.5v, (Hi, Lo) voltage is as seen in the videoI went to Honeywell to look for it, but unfortunately I found nothing new.I'm guessing it was made in 1989, maybe there aren't detailed records or it's an OEM productI don't know if it's the pressure sensor that's damaged, or if the blue potentiometer on the circuit board was adjusted incorrectly.(A closer look,R1102-NULL, R1104-XD BAL, R1116-ZERO, R1123-VB SET have been adjusted,Only R1109-TC and R33 have no trace of adjustment)I can't find any datasheet for this pressure sensor

author: daisizhou
author_rank: Super Contributor
timestamp: May 15, 2025, 11:14:04 am
content: So far, I have followed the instructions in the manual,The pressure module parts were tested separately,That is, V/F converter,I input "10" and "20" respectively, and the pressure part can stably display 378 and 375.I did not adjust any of the blue potentiometers because I do not know how to adjust them

author: daisizhou
author_rank: Super Contributor
timestamp: May 15, 2025, 09:39:48 pm
content: I tested the resistance between the pins of the pressure sensor in detail.

author: Poroit
author_rank: Frequent Contributor
timestamp: May 16, 2025, 09:48:13 am
content: Page 8-5 gives you a good explanation of the flow sensor type.The manual states that the Flow sensor is a Silicon strain gauge type so your resistances are probably OK.chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://vishay-straingauge.com/pdf/strain/precision-strain-gages-sensors-1.pdfchrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://docs.micro-measurements.com/?id=8690You should be able to test if it is OK by :1.Disconnect both existing tubes and attach a length of Silicon or PVC Tubing to the P+ Port that you can gently blow into.2.Power up the PCB and measure the signal output 8-5-2.3.See if the output changes when you blow into the tubing.

author: daisizhou
author_rank: Super Contributor
timestamp: May 16, 2025, 12:21:34 pm
content: Quote from: Poroit on May 16, 2025, 09:48:13 amThanks.As you said, I disconnected the line,Input positive pressure to the P+ port, or input negative pressure to the P- port.Then enter "30" to enter the V/F converter interface,Seeing the data change,Up to more than 2000.When I remove the P+, ​​P- pressure,That is, leave the pressure sensor empty in the air.On the V/F converter interface, see the number displayed is 10, and slowly decrease.According to the manual Page 10-6, the correct data should be 375+10.The voltage between TP2-TP10 should be 0.005vdc.Looks like the base point is offset.(The reference point of common pressure sensors will not shift.)

author: jwet
author_rank: Frequent Contributor
timestamp: May 16, 2025, 03:58:28 pm
content: You might try looking for "Sensym", its a Honeywell brand that they bought a while back and consolidated all thea OEM pressure sensors. They're in Freeport Illinois away from the HQ. The Microswitch brand goes back a long, long way. Its probably house numbered anyway but its a shot. You might be able to talk to a gray beard applications guy there.

author: daisizhou
author_rank: Super Contributor
timestamp: May 17, 2025, 02:56:55 am
content: Quote from: jwet on May 16, 2025, 03:58:28 pmThanks.Is there any contact information for this white-bearded application engineer? For example, emailI found a "Sensym" document.But it seems that no similar pressure sensor was found insidehttps://archive.org/details/SenSym-Solid-StatePressureSensorsHandbook1994OCR/page/n1/mode/2up

author: daisizhou
author_rank: Super Contributor
timestamp: May 17, 2025, 03:14:08 am
content: I found that the pressure sensor seems to have poor thermal stability,The pressure variation linearity seems to be normal.In order to better explain, I drew a simple illustrationOn page 10-8 of the manual，V/F Converter 250-500，TP2-TP4 Voltage 0 +/-.005vdcI tried to adjust R1102，Discover and start comparing,After warm-up, it can be stabilized at 375+10，TP2-TP4 voltage also seems to be stable at 0 ~+/-.005vdc,But after powering on, the V/F converter seems to reach around 630,The voltage also seems to exceed the standard setting.I don't know which adjustment is the best choice

author: daisizhou
author_rank: Super Contributor
timestamp: May 17, 2025, 07:19:58 am
content: Does anyone know,Can I use an SCX15DNC pressure sensor instead?https://www.alldatasheet.com/datasheet-pdf/view/282914/SENSORTECHNICS/SCX15DNC.html

author: Poroit
author_rank: Frequent Contributor
timestamp: May 17, 2025, 07:58:40 am
content: Is the Output of REF01 stable during your testing?Section 2. Pages 8-5 & 8-6 gives a description of the DP PCB.Do you have a suitable DC source to simulate the DC output ?

author: daisizhou
author_rank: Super Contributor
timestamp: May 17, 2025, 08:20:08 am
content: Quote from: Poroit on May 17, 2025, 07:58:40 amI got four 4K resistors and simulated a bridge resistor network.Then I connected these 4 resistors to the pressure sensor position on the PCB board.It is found that the HI and LO voltages will not drop significantly.Similarly, input "30" to enter the V/F converter interface, and the data is also stable.So I judge that the pressure sensor has thermal stability defects

author: Poroit
author_rank: Frequent Contributor
timestamp: May 18, 2025, 01:06:57 pm
content: Clever....well done.SCX15DNC looks electrically compatible but hard to tell without the specs on the Microswitch DP.According to Google ...Most of us can blow a pressure between 2.0 to 3.5 PSI.Ref Page 1-4 of the manual. Do any of the sensors in RT-202 look similar to RT-203?I could not find any details on mV/V for a 4K Strain Gauge Bridge.I have mainly worked with 350ohm @ 2mV/V, so 20mV output with a 10V Excitation.What mV output did you measure from your 4Kohm simulated bridge?

author: daisizhou
author_rank: Super Contributor
timestamp: May 18, 2025, 01:45:44 pm
content: I drew a schematic, hoping it would help with the analysis.(If you find any errors please let me know, thanks)The RT-202 sensor looks the same as the RT-203,But their functions seem to be somewhat different,The RT-202 pressure sensor interface is directly connected to the external interface，The user can input positive or negative pressure at P1 or P2 port.But the RT-203 pressure sensor is connected to the front and rear ends of the "air resistance",It is used together with "air resistance" to test gas flow.There is also a solenoid valve for switching between high and low flow rates.The PCB amplifier circuit is normal.There is a fault inside the pressure sensor itself.Do you need a video of me testing the 4K resistor bridge? If so please let me knowI can confirm that the pressure sensor itself is faulty.Maybe it's due to aging.

author: Poroit
author_rank: Frequent Contributor
timestamp: May 19, 2025, 08:42:07 am
content: It may have failed due to age, overpressure or moisture.Are you going to seriously consider retrofitting another brand of sensor?The manual only gives a flow range of 0-180 lpm for RT203 but no mention of its Proof Pressure to help you easily select a replacement.The Vs for the SCX Series is 12V DC but I am sure you can modify the PCB to suit.Do you have access to equipment to calibrate the RT200 if you replace the DP Transducer?

author: daisizhou
author_rank: Super Contributor
timestamp: May 19, 2025, 09:59:55 am
content: Quote from: Poroit on May 19, 2025, 08:42:07 amYes.If it can be perfectly compatible with the replacement, why not?I'm used to using the RT-200, although it's quite old.Yes.RT-203 is a flow module。There is a high flow fixed air resistance (High range) and a low flow fixed air resistance (Low range) inside.Switching via a solenoid valve.Finally, the pressure difference is converted into flow value.The SCX series pressure sensor is what I have on hand. I just found it.If there is a more perfect alternative, I will choose another model.I have equipment to calibrate the RT200, such as a FLUKE vt650 (from a friend), a Respical T300As long as there is a suitable pressure sensor,And the correct calibration steps,Success is just a matter of time,Of course, this is also inseparable from the help of all my friends.

author: daisizhou
author_rank: Super Contributor
timestamp: May 19, 2025, 02:12:29 pm
content: I used a digital multimeter to measure the voltage values ​​of the four pins of the pressure sensor.May I know the definition of each of them?How do I know their respective definitions (V+, V-, S+, S-)?

author: daisizhou
author_rank: Super Contributor
timestamp: May 20, 2025, 04:29:00 am
content: This is my guess about the pin definition of the pressure sensor.And the pressure value corresponds to the 【（S+）-（S-）】,【 HI-LO】 voltage data。

author: Poroit
author_rank: Frequent Contributor
timestamp: May 20, 2025, 07:20:23 am
content: Yes, I agree with you....Why Not.You have done all the hard work so Full Steam Ahead.Please let us know if the DP Sensor replacement and recalibration are successful.

author: daisizhou
author_rank: Super Contributor
timestamp: May 20, 2025, 07:31:42 am
content: Quote from: Poroit on May 20, 2025, 07:20:23 amNo, I don't know how to choose a pressure sensor.In other words, I don't know which model of pressure sensor is the best match for RT-203,That is, it can be interchanged with "MICRO SWITCH"I drew the circuit schematic from the PCB,But I don't understand the circuit principle.I am not good at analyzing circuit schematics.Can you know the functional purposes of R1109 (TC), R1102 (NULL), R1104 (XD BAL), R1116 (ZERO), and R1123 (VB SET)?

author: daisizhou
author_rank: Super Contributor
timestamp: May 20, 2025, 01:08:57 pm
content: From the data, it seems that the zero point of the pressure sensor has shifted by 0.31mv.I see a "TC" symbol on the PCB board. Is this used to adjust temperature drift?There is also a "ZERO" logo,Is it used to adjust the zero position?

author: Poroit
author_rank: Frequent Contributor
timestamp: May 21, 2025, 08:28:17 am
content: R1111 is connected directly across Pins 2 & 4 which is the DP Sensor output.XD BAL is probably the abbreviated form for Transducer Balance (xducer)You could determine the range of the replacement DP by looking at the RT200 uses outlined in 1. Introduction A. General.I assume it can be used to test Medical Oxygen supplies which are regulated to 50-55 PSI, so the Flow Sensor must be rated higher than that.Maybe the DP Transducer in RT-203 is the same as the High Pressure DP in RT-202.Your Fluke VT650 looks like a modern day equivalent of RT-200 so compare specs.

author: daisizhou
author_rank: Super Contributor
timestamp: May 21, 2025, 08:43:40 am
content: Quote from: Poroit on May 21, 2025, 08:28:17 amThanks.Do you mean that by adjusting R1111 (XD BAL), I can adjust the offset of the pressure sensor output zero?That is 0.15mv-0.33mv[For compensation]。If R1111 (XD BAL) is to adjust the balance, then what is R1116 (ZERO)?And R1123 (VB SET). looks like some kind of setting selection.The interior of RT-202 is shown below,Although they look the same, the data sheet is not available.I disassembled the RT-200 and this is the connection.--https://www.ebme.co.uk/forums/ubbthreads.php/topics/78352/3The Fluke VT650 is different from the RT-200, at least the sensor is completely different.I think the FLUKE VT Plus HF is more like the RT-200. Please see the picture.Differential pressure sensors are used to convert flow

author: daisizhou
author_rank: Super Contributor
timestamp: May 21, 2025, 11:10:31 pm
content: Quote from: Poroit on May 18, 2025, 01:06:57 pmHi You mentioned "350ohm @ 2mV/V, so 20mV output with a 10V Excitation."Is 350ohm the output impedance?--[(S+)-(S-)] Resistance valueWhat does 2mV/V mean?Is 20mV the maximum output voltage difference of the pressure sensor [(S+)-(S-)]?"10V Excitation"Is it the voltage connected to the pressure sensor [（VCC）-(GND)] power supply?

author: Poroit
author_rank: Frequent Contributor
timestamp: May 22, 2025, 08:59:32 am
content: R1123 VB SET ......connected to the Trim of the REF01PrecisionVoltage Reference and is used to adjust the output voltage.R1111 XD BAL....I suggest this is used to Zero the DP Transducer when both ports are open to atmosphere.350 ohm is the Resistance of each Strain Gauge used in the Bridge.2mv/V means for every 1 V of Excitation the Bridge Outputs 2mV when strained to it rated capacity. (see attached)

author: daisizhou
author_rank: Super Contributor
timestamp: May 22, 2025, 11:13:03 am
content: Quote from: Poroit on May 22, 2025, 08:59:32 amThanks.I sent the circuit schematic to "DeepSeek" and asked "DeepSeek" what these adjustable resistors are used for."DeepSeek" gave me the following answer, which seems reasonable----------------------------------------------------------------------------------------------------------------------------------------------------R1102 (NULL): This resistor is connected to the inverting input of an operational amplifier (U1B). It is likely part of a feedback or input network designed to nullify or balance out any inherent offset voltage of the op-amp or the preceding stage. This ensures that when the intended input is zero, the output is also accurately zero, which is critical for precise measurements.R1123 (VB SET): This resistor is part of a voltage divider network connected to the "VBET" line. "VBET" most likely stands for "Voltage Bias Set" or "Voltage Buffer Enable Threshold." Therefore, R1123's purpose is to set a specific bias voltage for a part of the circuit, possibly for a sensor or an amplifier stage, ensuring it operates correctly within its specified voltage range.R1109 (TC): This resistor is found in the feedback path of an operational amplifier (U1A). The label "TC" typically stands for "Temperature Compensation". Its role is to adjust the circuit's gain or offset to counteract drifts caused by changes in temperature, especially important for sensitive components like pressure sensors, to maintain accuracy over a range of operating temperatures.R1104 (XD BAL): This resistor is connected to the non-inverting input of an operational amplifier (U1A). The label "XD BAL" likely refers to "Transducer Balance" or "Cross-Differential Balance". Its primary function is to balance the differential inputs of the amplifier, minimizing common-mode errors and ensuring accurate amplification of the differential signal from a sensor (like the "PRESSURE SENSOR" shown nearby).R1116 (ZERO): This resistor is connected to the inverting input of an operational amplifier (U1C). The label "ZERO" indicates that its purpose is to adjust the output of that stage to zero when there is no intended input or when the input is at its baseline level. This allows for a precise "zero-point" calibration of the circuit, preventing false readings or offsets.------------------------------------------------------------------------------------------------------------------------------------------------------Combined with the actual situation, I guessed the following explanation:R1102 (NULL): As the manual says on page 10-6,Adjust R1102 to ensure [HI-LO] voltage remains 0 +/-.005VDCR1123 (VB SET):Adjust R1123, the voltage of 9.3v for the pressure sensor P1 pin may be a constant currentR1109（TC）:Correction of [HI-LO] voltage changes caused by temperature changesR1104 (XD BAL)：It may be used to adjust the zero voltage of the pressure sensor [S+/S-]R1116 (ZERO)：It seems to be a duplicate of R1104 (XD BAL), which may be the zero adjustment when the sensor is not loaded.{My guess}

author: daisizhou
author_rank: Super Contributor
timestamp: May 22, 2025, 10:59:41 pm
content: I disassembled the PCB circuit board inside the RT-202 pressure module.It looks like it has one more diode than the RT-203 flow module.I used the same method to test the voltage of the pressure sensor [(S+)-(S-)] in the RT-202 pressure module.It was found that the voltage [(S+)-(S-)] was also 0.32v when no pressure was input.Then the pressure sensor on the RT-203 flow module is not damaged, it may have an inherent voltage biasIt seems that only appropriate adjustments to R1116 (ZERO) and R1109 (TC) are needed to restore normal operation.I am not sure about R1116 (ZERO) and R1109 (TC). Should I adjust one or both?

author: Poroit
author_rank: Frequent Contributor
timestamp: May 23, 2025, 09:23:51 am
content: R1109 TC would be associated with the Thermistors mentioned on Page 8.6 Section C. 3.Maybe the thermistor resistances has drifted but you may be able to identify the type and check it. The manual says there are two, so they may be in a Wheatstone Bridge type circuit.If you are happy that XD is adjusted correctly, after measurements, then adjust ZERO.Make a note of how far you turn the adjuster so you can always set it back to where it was.

author: daisizhou
author_rank: Super Contributor
timestamp: May 23, 2025, 10:24:11 am
content: Quote from: Poroit on May 23, 2025, 09:23:51 amNo.The A3A3A2 mainboard is faulty or needs adjustment.My schematic is also drawn A3A3A2 motherboard.R1109 TC is also on the A3A3A2 motherboardPage 8.6 Section C. 3. Refers to A3A3A1 motherboardI have not made any adjustments to the R1104 (XD BAL) as I do not know exactly how to adjust it.In other words, I am worried that if I make adjustments, I may make irreversible mistakes.It would be great if someone could analyze R1116 (ZERO) and R1109 (TC) from the schematic.*The schematic diagram U1101 (OP11EY) has been modified to correct an error*

author: daisizhou
author_rank: Super Contributor
timestamp: May 24, 2025, 10:19:04 pm
content: I took a video, please watch it

author: Poroit
author_rank: Frequent Contributor
timestamp: May 25, 2025, 07:02:12 am
content: Sorry...I misread thermistor association.R1104(XD BAL) is used to trim the output of the Flow DP Transducer as per attached.https://tacunasystems.com/knowledge-base/load-sell-summing-junction-boxes-signal-trim-and-excitation-trim/Page 8-5 C.2. "Others temperature compensate". this would apply to the LM346N.I assume as per method "TEMPERATURE EFFECT ON THE GBW OF LM346N"

author: daisizhou
author_rank: Super Contributor
timestamp: May 25, 2025, 08:42:26 am
content: Quote from: Poroit on May 25, 2025, 07:02:12 amHave you checked out the video I shot on the 31st floor?So far, I have ruled out the possibility that R1102 (NULL) and R1123 (VB SET) need to be adjusted.However, R1109 (TC), R1104 (XD BAL), and R1116 (ZERO) all seem likely to be adjusted.I can't decide which of the three is most appropriate.Can you parse the clues from the circuit schematic?Read Page 8-5 C.2. Adjust R1109 (TC) to reduce the possibility. The remaining ones are still R1104 (XD BAL), and R1116 (ZERO)

author: Poroit
author_rank: Frequent Contributor
timestamp: May 26, 2025, 06:36:30 am
content: I watched the videos.I would adjust R1104 (XD BAL) as this should Zero the Flow DP Transducer Output.( Both DP tube connections open to atmosphere)Then measure across Pins 2 & 3 of LM307 and use R1116 (Zero) to adjust to zero.

author: daisizhou
author_rank: Super Contributor
timestamp: May 26, 2025, 08:13:07 am
content: Quote from: Poroit on May 26, 2025, 06:36:30 am( Both DP tube connections open to atmosphere)You mean to measure (S+, S-), adjust R1111 (XD BAL) until the display returns to zero,Then measure LM307 (P2, P3), adjust R1116 (ZERO) until the display is zero?In addition, I see from the schematic diagram that if R1111 (XD BAL) is adjusted, it seems to be related to LM346 (P2, P1),That is, the VCC and GND of the pressure sensor(Here I marked it as VCC and GND, but it is actually V+ and V-),In other words, they are the values ​​set by R1123 (VB SET)Adjusting R1116 (ZERO) also has similar correlation effects.In the end I didn't dare to adjust them at will, are you sure you need to adjust them (XD BAL and R1116(ZERO))?

author: Poroit
author_rank: Frequent Contributor
timestamp: May 28, 2025, 03:42:38 am
content: Yes....to be clear....Use your multimeter to measure across S+ and S-.You have already proven by your DP Flow Sensor simulation and your measurements that the sensor has a Zero Offset so why not adjust it.Plus....you have all the necessary test gear to calibrate the RT200 and you can always readjust to old values if you find some unforeseen problem.

author: daisizhou
author_rank: Super Contributor
timestamp: May 28, 2025, 04:31:12 am
content: Quote from: Poroit on May 28, 2025, 03:42:38 amOK. Thanks.I'll try to adjust them.The reason why I dare not try it easily is that,R1102 (NULL), R1123 (VB SET), R1109 (TC), R1104 (XD BAL), R1116 (ZERO) These seem to be used to adjust the linearity of the pressure sensor,The calibration data of the RT-200 host is stored in the EEPROM. I don't know how to adjust the data in this EEPROM yet.

author: daisizhou
author_rank: Super Contributor
timestamp: May 28, 2025, 06:12:42 am
content: Hi PoroitI adjusted the R1104 (XD BAL) and found that S+ and S- would be as expected and would show zero after adjustment.But the results did not improve.HI and LO voltages still exceed 0.005vdc,Similarly, at the 30 interface, the v/f converter starts to drop at 780(in other words，I adjusted R1104 (XD BAL) after warming up the engine for 20 minutes. Although it can be displayed as zero, as soon as I restart, all previous adjustments are invalid and it will not display zero.)Adjusting R1116 (ZERO), not as expected, because LM346 (P2, P1) always shows 0.998mv-1.002mv,Cannot display zero position,Finally, I restored R1116 (ZERO) to its original setting position.(Maybe the LM346 (P2, P1), the test point selection is incorrect, or other reasons, I still can't observe any connection between adjusting it and "ZERO")In my opinion, adjusting the zero position has no real effect.Because the temperature drift of the pressure sensor must exist.We should be looking for temperature compensation adjustment, not zero adjustment,I drew a simple picture, I hope you can understand what I meanI wonder if R1109(TC) is an adjustable resistor for temperature drift compensation adjustment as I expected.It would be great if you could analyze the circuit schematic and verify my guess, thanks

author: daisizhou
author_rank: Super Contributor
timestamp: May 29, 2025, 08:06:01 am
content: From the latest circuit schematic, it can be seen that,R1117_VB_SET is used to regulate the output voltage of pin 6 of U1104,But R1116_ZERO seems to also adjust the voltage,What I mean is that it has nothing to do with its standard 'ZERO',And it seems that their true purpose has been repeated,I don't know why?I don't know the basis for adjusting R1104_XD_SAL. It looks the same as R1102-NULL, which balances the input signals of U1101.1 and U1101.4R1109_TC looks like a reverse amplifier, and the final signal goes to n14, which means it enters pin 9 of "1698-99-0". I don't know what will be sent next

author: Poroit
author_rank: Frequent Contributor
timestamp: May 30, 2025, 05:57:06 am
content: "I got four 4K resistors and simulated a bridge resistor network.Then I connected these 4 resistors to the pressure sensor position on the PCB board.It is found that the HI and LO voltages will not drop significantly.Similarly, input "30" to enter the V/F converter interface, and the data is also stable."Have you rechecked via the above method?Does adjusting R11116 zero the Output of LM307J Pin 6 ?Is the Vout of REF01J stable during your testing?Readjust R1104 (XD BAL) after warm up and tap the all trimpots with the handle of a screwdriver and note changes to measurements.

author: daisizhou
author_rank: Super Contributor
timestamp: May 30, 2025, 07:09:48 am
content: Quote from: Poroit on May 30, 2025, 05:57:06 amYes.However, the pressure sensor always has voltage fluctuations caused by temperature drift, see the picture.I compared the RT-202 module with the RT-203 module, and it looks like the RT-203 compensation is not working.(In other words, the temperature drift compensation does not match)*Please watch this video. The HI-LI voltage reaches 0.0000 and seems to start to rise again.(https://youtu.be/SUkBNAbheC4)*Do I need to reconnect the 4K resistor, simulate the test, and shoot a video?Quote from: Poroit on May 30, 2025, 05:57:06 amI am measuring the voltage difference between pin 2 and pin 3 of the LM307J. Do you mean for me to measure the voltage of pin 6 of the LM307J? Which pin should I choose for "GND" (black probe connection of the DMM)?*So far, I have tested it according to the attached picture "lm307-p6test" and the voltage value I see is always 0*Quote from: Poroit on May 30, 2025, 05:57:06 amI only adjusted R1111 (XD BAL) and R1116 (ZERO), and found that the pressure sensor VCC and GND voltage changed from 9.3v to about 9.1v now. I measured the pressure sensor pin 1 and pin 3.Quote from: Poroit on May 30, 2025, 05:57:06 amAdjust R1104 (XD BAL) and measure the 2nd and 4th pins of the pressure sensor.During the adjustment process, it can be clearly seen that the adjustment has taken effect, and the voltage difference between them gradually becomes 0, but as long as it is restarted once, the effect of the last adjustment disappears completely, and it looks like it has not been stored.

author: Poroit
author_rank: Frequent Contributor
timestamp: May 31, 2025, 07:30:48 am
content: I suggest you try measurements a couple of steps at a time to build up a calibration procedure :1. Power up the RT200 and allow warmup time.2.REF01J is a 10V Precision Reference. Using your most accurate Multimeter, adjust VB SET and adjust VOUT Pin 6 to 10V. (Record Value)3. Adjust R1104 (XD BAL) to zero the Flow DP Transducer Output Pins 2 & 4.( Record Value)4.Recheck 2.5.Power down RT200.6.After 30 minutes, Power up RT200 and measure/ record as above 2 & 3.

author: daisizhou
author_rank: Super Contributor
timestamp: May 31, 2025, 08:54:23 am
content: Quote from: Poroit on May 31, 2025, 07:30:48 amAt present, I measured the voltage between the two pins of C1105 and it is 8.473v,R1117(VB SET) and R1116(ZERO) It seems to be used to adjust voltage or current.The input impedance of the pressure sensor is 5.2k and the output impedance is 3.3k.I roughly calculated that the current is about i=8.473/5200~1.63ma.I looked for a similar pressure sensor with an input impedance of 5.2k.(Please see the attached manual)Input excitation ~1.5ma Max~2maIf I adjust R1117 (VB SET) to 10V, then the current will reach 4ma,I'm worried about burning out the pressure sensor.

author: daisizhou
author_rank: Super Contributor
timestamp: June 01, 2025, 10:11:48 am
content: I tried to adjust R1109(TC)，But it didn't have any effect,It seems that the temperature drift has nothing to do with R1109 (TC).I'm a bit lost, I don't know how to compensate for the sensor temperature drift.If the temperature drift of the pressure sensor can be compensated, then this fault should be easy to eliminate.

author: Poroit
author_rank: Frequent Contributor
timestamp: June 02, 2025, 07:37:31 am
content: Does RT-202 PCB also have a REF01J ?If yes ,then measure its output for comparison.

author: daisizhou
author_rank: Super Contributor
timestamp: June 02, 2025, 07:57:44 am
content: Quote from: Poroit on June 02, 2025, 07:37:31 amYes, the only difference is the addition of a diode.Please see the picture.I have measured the voltage of RT-202 pressure sensor and it is 9.1v

author: daisizhou
author_rank: Super Contributor
timestamp: June 02, 2025, 08:05:31 am
content: Do you need me to re-shoot the video of the changes in S+\S- and HI\LO voltages of RT-202 and RT-203 and provide it to you for analysis?Now I'm a little lost? I can't figure out where the problem isFrom the previous video, we can see that the RT-202 (S+\S-) changes by about 0.15mv from startup to stability.The change of RT-203 (S+\S-) from startup to stability is about 0.35mv.I don't know if this is caused by the aging of the pressure sensor.

author: Poroit
author_rank: Frequent Contributor
timestamp: June 03, 2025, 07:25:07 am
content: You need to confirm if the DP sensor is actually faulty.If you have a reasonable quality Bench Top power supply, then Bench test the suspect DP transducer while removed from the PCB.With both Pressure Ports open:1.Apply 8.473 VDC to supply and monitor the output for 10 minutes.Apply suitable Pressure to P+ Port.2.Monitor the output for 10 minutes.If both tests are stable, warm the DP Sensor slightly with a Hot Air Gun and see if output changes substantially.

author: daisizhou
author_rank: Super Contributor
timestamp: June 03, 2025, 09:31:49 am
content: Quote from: Poroit on June 03, 2025, 07:25:07 amOK,Please see the video, I did the test as you described.The voltage increased from 0.15mv to 0.53mv, and the time lasted about 10 minutes.I don't know if this voltage drift is normal.

author: daisizhou
author_rank: Super Contributor
timestamp: June 04, 2025, 12:36:10 am
content: Hallo everyone.I have good news for you. I scratched off the sticker and I saw a model number "125PC05D1" on it.I know there are sellers on EBAY selling the same model of pressure sensor,However, I am in a country or region where it is not possible to shop on EBAY conveniently and quickly.In addition, the high shipping cost is much higher than the price of the pressure sensor itself.So I can only look for a compatible pressure sensor to use,If anyone can tell me a perfectly compatible model that would be great, thank you in advance

author: daisizhou
author_rank: Super Contributor
timestamp: June 05, 2025, 04:37:41 am
content: From the test data on the 49th floor, we can see that the voltage drifted by about 0.38mv.

author: Poroit
author_rank: Frequent Contributor
timestamp: June 05, 2025, 05:11:35 am
content: Is that definitely 30mV drift?According to 8060A manual, the 200mV Range has .01mV resolution.If it is 30mV then it is faulty.

author: daisizhou
author_rank: Super Contributor
timestamp: June 05, 2025, 06:25:17 am
content: Quote from: Poroit on June 05, 2025, 05:11:35 amSorry.I miscalculated.It looks like it is offset by 0.38mv (0.15-0.53=0.38).It seems that there is no malfunction.Do you know how to adjust R1116(ZERO)?I mean does adjusting it have anything to do with "ZERO"?I don't know why, but HI-LO always has voltage fluctuations of over 130 mVI re-solder 4 5k resistors to simulate the pressure sensor. Please see the video. The voltage fluctuation still exists. I don't know where this fluctuation comes from and how to eliminate it.

author: Poroit
author_rank: Frequent Contributor
timestamp: June 09, 2025, 06:52:39 am
content: 1.Connect your multimeter to Pins 6 & 4 of REF01.2. Apply Power.3. Post a video of the result.High output accuracyREF01: 10.0 V, ±0.3% maximum= +/-30mV @ 10V

author: daisizhou
author_rank: Super Contributor
timestamp: June 09, 2025, 01:14:49 pm
content: Quote from: Poroit on June 09, 2025, 06:52:39 am

author: Poroit
author_rank: Frequent Contributor
timestamp: June 10, 2025, 06:40:57 am
content: Have you studied AND UNDERSTAND the datasheet for REF01?From your video we see that there is approximately +180mV variation over the duration of your test and that is way outside the stated accuracy of the device.Refer Table 7 attached, Vout Low Limit.Repeat the test and video but adjust VB Set so that Pin 6 & 4 measure 10VDC.

author: daisizhou
author_rank: Super Contributor
timestamp: June 10, 2025, 07:54:31 am
content: Quote from: Poroit on June 10, 2025, 06:40:57 amThanks.I only know that REF01 is a 10 volt voltage reference chip, currently in adjustable output mode, with a maximum current of 20ma.I tried adjusting R1117 (VB SET)，But the voltage always remains around 8.47V, I don't know why.It seems to be affected by the feedback of LM307 and LM346N (U1102.1) op amps.I don't know how to test further.

author: Poroit
author_rank: Frequent Contributor
timestamp: June 11, 2025, 05:11:53 am
content: Remove the REF01 from the PCB and test it Out of Circuit as per Fig 35 and Table 7.

author: daisizhou
author_rank: Super Contributor
timestamp: June 11, 2025, 07:18:56 am
content: Quote from: Poroit on June 11, 2025, 05:11:53 amI connected the circuit as shown in the figure, input 18vdc voltage, adjusted the 10k adjustable resistor, and the output voltage was between 9.74v and 9.96v

author: Poroit
author_rank: Frequent Contributor
timestamp: June 12, 2025, 04:11:32 am
content: Was the REF01 Voltage Output stable during your testing or did you still have the 180mV drift ?

author: daisizhou
author_rank: Super Contributor
timestamp: June 12, 2025, 04:59:23 am
content: Quote from: Poroit on June 12, 2025, 04:11:32 amREF01 voltage output is very stable, no 180mv drift.It just can't reach the minimum voltage of 9.7v and the maximum voltage of 10.05vHow do I proceed next?

author: Poroit
author_rank: Frequent Contributor
timestamp: June 13, 2025, 05:31:32 am
content: The REF01 datasheet shows Output Adjustment Range is typically +/- 3.3%.( I assume range) +/-330mV.The REF01 you tested is probably OK but something else in the circuit is loading it down.(excess current) Can you source replacement if needed?Reinstall the REF01 and unsolder one end of various components ...eg...R1104.....then check VOUT to see if it increases.You have three amplifiers on that PCB ...OP11, LM307J, LM346N.Try and determine which section is loading down the REF01.

author: daisizhou
author_rank: Super Contributor
timestamp: June 13, 2025, 07:30:11 am
content: Quote from: Poroit on June 13, 2025, 05:31:32 amYes, I can replace all common electronic components except the 125PC05D1 pressure sensor and 1698-99-0Quote from: Poroit on June 13, 2025, 05:31:32 amI tried to separate the LM307, OP11, and LM346N individually, and the vout voltage did not seem to change significantly, it was still the same as beforeQuote from: Poroit on June 13, 2025, 05:31:32 amR1104??You mean R1114?It looks like a component is loading too much current, causing the voltage to be pulled down,But I measured most of the resistors and found that the resistance values ​​were almost normal.Is it related to the incorrect settings of R1123 (VB SET) and R1116 (ZERO)?I don't know how to check next

author: Poroit
author_rank: Frequent Contributor
timestamp: June 14, 2025, 04:59:33 am
content: I meant R1104......anything connected to VOUT.Even lift one end of C1105.RT202 is identical to RT203 so use it for comparison measurements.It did seem strange that you could not adjust REF01 above 10V as it is a 10V Reference, so maybe invest in a replacement to rule it out completely.

author: daisizhou
author_rank: Super Contributor
timestamp: June 14, 2025, 05:34:18 am
content: I have an idea,I removed REF01,Connect a wire to each of the VOUT pin and GND pin of REF01, that is, pin 6 and pin 4.Then use an external power supply to provide a 10.000v or 8.677v power supply separately.(Because only in this way can we see through the external power supply how much working current REF01 needs to bear in actual operation)The above is my idea. I don't know if it is feasible.I found that REF01 2nd and 4th, that is, the input voltage seems to be fluctuating, please see the videoI found a LH0070-OH，It looks like it is also a 10v voltage reference,Is a replacement test needed?(It may be difficult to adjust the voltage output)

author: Poroit
author_rank: Frequent Contributor
timestamp: June 16, 2025, 08:54:06 am
content: Your last video shows approximately +90mV change as the unit warms up.Read section called LINE REGULATION of the REF01.Worst case for H Grade is 150ppm/V so not a problem for your testing.You could insert DC mA meter (multimeter) in series with Pin 6 to see how much current is being drawn.Element 14 has REF01.

author: daisizhou
author_rank: Super Contributor
timestamp: June 16, 2025, 09:14:57 am
content: As you can see in the video,The initial power supply of 29.18v is very stable,The negative terminal of REF01 is connected to a common port(Green logo),19.712v has fluctuations.I don't know how to check, they all seem to be normal

author: daisizhou
author_rank: Super Contributor
timestamp: June 16, 2025, 12:47:32 pm
content: Please see that R1116 (ZERO) looks similar to the 50k resistor with zero adjustment in the picture,However, in reality, the DUP4 position of output 1 of LM346 is always around 10.39v-9.4v and cannot be adjusted to zero position.So how to adjust R1116 (ZERO) correctly has been bothering me all along

author: daisizhou
author_rank: Super Contributor
timestamp: June 18, 2025, 02:52:03 am
content: I compared RT-202 and RT-203,Two PCBs were found to be almost identical, with the only difference being R1101 and a glass diode.R1101 inside RT202 seems to be a "DALE" and "RN55D" series resistor.And R1101 in RT-203 is a common resistor with 100 ohms and 50 ppm.Is it possible that this subtle difference is causing voltage drift fluctuations?------------------------------------------------------------------------------------------------------------------------------------------------------I tried to replace R1101 with a 0.1% 100 ohm resistor, but it didn't improve

author: daisizhou
author_rank: Super Contributor
timestamp: June 19, 2025, 12:31:14 pm
content: Hi PoroitI checked the resistance value of the resistor again and did not find any offset resistance. I don't know how to proceed with the next testing step. Do you have any better suggestions?

author: Poroit
author_rank: Frequent Contributor
timestamp: June 20, 2025, 06:06:33 am
content: Read Again.....Replies #62,64,66 and test further.Purchase replacement REF01.

author: daisizhou
author_rank: Super Contributor
timestamp: June 21, 2025, 11:02:54 pm
content: Quote from: Poroit on June 20, 2025, 06:06:33 amI disconnected R1130 in the circuit and removed jumper J1101,Continue to measure the voltage value of C1105.The circuit is shown in Figure 22 below,Please watch test video 1I removed the LM307N and LM346N, see test video 2Finally I removed the LM307N, see test video 3

author: picburner
author_rank: Frequent Contributor
timestamp: June 22, 2025, 04:34:06 am
content: In «Reply #67 on: June 16, 2025, 09:14:57 am»:The voltage measured across R1128 is (29.18V - ~19.712V) ~9.468V, the resistor is 33Ω 1/4W and therefore it would dissipate ~2.7W with a current of ~287mA!Something is wrong with that measurement.

author: daisizhou
author_rank: Super Contributor
timestamp: June 22, 2025, 07:22:21 am
content: Quote from: picburner on June 22, 2025, 04:34:06 amI measured the 29.18v on the top of R1128 by connecting it to GND, not the common terminal.That is the GND on the left side of R1129.I re-measured after connecting the common,Please see the attached picture "66"