Help identify the pressure sensor - Page 1
Forum section: electronics / repair

author: daisizhou
author_rank: Super Contributor
timestamp: March 27, 2021, 12:48:31 pm
content: There are 3 pressure sensors on the test air pressure detector,I took a picture separatelyNB1 Looks like Sensym 926 SZ75153,metal shell,There are three wires in the interface.NB2 I only see MICRO SWITCH USA,Number is K042NB3 I only see MICRO SWITCH USA,Number is J1238 8914Someone may know that this is a Honeywell model,I try to contact Honeywell service personnel,But gives the answer as shown belowI probably know this is the equipment produced in 1989,Can be used for medical related,Test air or oxygen dry gas,Pressure and flowI hope people who know can tell me the model or the model used in place of it,Or its successor model

author: daisizhou
author_rank: Super Contributor
timestamp: March 28, 2021, 12:04:14 am
content: Help, friends who know their model please tell me, thank you

author: amyk
author_rank: Super Contributor
timestamp: March 28, 2021, 03:27:29 am
content: Look in here?https://archive.org/details/SenSym-Solid-StatePressureSensorsHandbook1994OCRQuoteYours looks like LX18XXDZ series, but is a custom part.

author: daisizhou
author_rank: Super Contributor
timestamp: March 28, 2021, 04:57:04 am
content: Thanks for the help.But I can’t open and browse this URLhttps://archive.org/details/SenSym-Solid-StatePressureSensorsHandbook1994OCRI can't find the reason

author: coromonadalix
author_rank: Super Contributor
timestamp: March 28, 2021, 07:10:26 am
content: https://archive.org/download/SenSym-Solid-StatePressureSensorsHandbook1994OCR/SenSym-Solid-StatePressureSensorsHandbook1994OCR.pdfa 96mb file

author: daisizhou
author_rank: Super Contributor
timestamp: March 29, 2021, 04:14:29 am
content: I'm very much obliged to you,Let me quickly find the model,It is indeed LX1820DZThis is the voltage value corresponding to my actual test pressureIf you can help me find another 2 micro switches,That would be perfectThanks again for your help

author: daisizhou
author_rank: Super Contributor
timestamp: March 29, 2021, 05:54:49 am
content: I measured this air pressure module,I guess this sensor has no magnification function,It relies on an external operational amplifier circuit to amplify the output.This is the clue i know

author: fzabkar
author_rank: Super Contributor
timestamp: March 29, 2021, 09:32:30 am
content: Are NB2 and NB3 switches, or are they pressure sensors made by Micro Switch USA?For example, here are two 3-pin Micro Switch pressure sensors, with signal conditioning (not yours):https://pdf.dzsc.com/1PC/141PC01G_1077424.pdfhttps://docs-emea.rs-online.com/webdocs/0025/0900766b80025ae3.pdfThe first sensor in this datasheet is a 4-pin Wheatstone bridge requiring an external constant current source:https://stevenengineering.com/Tech_Support/PDFs/31PRSS.pdf

author: daisizhou
author_rank: Super Contributor
timestamp: March 29, 2021, 10:07:47 am
content: They are pressure sensors.But mark "micro switch" on the shell.I checked the housing of this pressure sensor, the pictures are on NB2 and NB3Did not see the exact specification modelI have viewed your PDF, but the shape is different.So I measured the entire circuit board, hoping to provide some clues

author: daisizhou
author_rank: Super Contributor
timestamp: March 29, 2021, 12:51:08 pm
content: NB2, NB3 pressure sensor,They don’t seem to have a gain amplification function.Amplified by an external operational amplifier.I guess it should be a bridge strain resistanceI hope to find its original record,Try to replace it or buy another model to replace it

author: amyk
author_rank: Super Contributor
timestamp: March 29, 2021, 01:44:36 pm
content: 180PC series looks like a close match...

author: daisizhou
author_rank: Super Contributor
timestamp: March 29, 2021, 02:13:15 pm
content: 180PC series looks a lot like,But only 3 lines of output,NB2 and 3 are 4-wire output.I think it should be a differential signal

author: fzabkar
author_rank: Super Contributor
timestamp: March 29, 2021, 05:41:13 pm
content: Here is an application circuit for a pressure sensor using a current source for biasing the Wheatstone bridge:https://www.notwired.co/datasheets/te/signal_conditioning_for_meas_pressure_sensors.pdfThis is the circuit I traced on a Western Digital hard drive with a 4-pin barometric pressure sensor:Code:VCC___ +.-|___|--. U25 /| |_| |__ /+|------. .-.' | || | ' .--------< | | | || '---||---' | Wheatstone | \-|--. | | || || | bridge | pin3 \| | | '-'| | / \ | | R19|| | R20 / \ | '----+| /|U26 | ___ | | | || /-|-----+-----|___|---------. .-. .-. | .-.+----< | ___ | | | | | | | || \+|-----+-----|___|-----. | | | | | | R49| || \| | | | '-' '-' | '-'.-. .-+-. R28 | |pin4| | pin2 | || | | | | '----+ U7 +----. | || | R113 .-. | | | | | | ==='-' | | --- C14 | .-. .-. | | GND| R37| | --- | | | | | | || '-' | | | | | | | |+-->|--> | | | '-' '-' | || '-+-' | | | | || D5 | | \ / | |v === | \ / | |GND | |pin1 | |amplified | | | |pressure | | | |output | '-------)------+| | |'-------------------' .-.| | R56| |'-'||===GNDU25 is the current source while U26 is a differential amplifier.