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I would like to be able to read values of two thermal couples and a pressure gauge using my raspberry pi. Recording the data and then sending it to a server at the end of the day.

I am using dual t/c thermal couples. Link for the them. https://www.omega.com/en-us/sensors-and-sensing-equipment/temperature/sensors/thermocouple-probes/p/ICIN-DUAL

I wanted to use this pressure sensor: http://www.revrobotics.com/rev-11-1107/

I was going to use a Raspberry Pi B with a breakout board: To read each value of voltage and then calculate real values in the code.

This breakout board: https://store.ncd.io/product/3-channel-4-20-ma-current-loop-receiver-16-bit-ads1115-i2c-mini-module/

If anyone can explain to me a better way to do this. I would be happy to listen I am confused on the breakout board because the board only has two connections per channel.

  • Not sure why you're calling the "3-Channel 4-20 mA Current Loop Receiver" a breakout board. And I would only expect 2 connections per channel, one for signal one for ground. It's a 3 channel board, so there are 6 connections total, this makes sense. – Glen Yates May 21 at 20:37
  • I am new to building things like this and guess I just got confused. So for the pressure sensor I can just ignore one of the cables? Using the ground and signal cable. – Max May 21 at 21:42
  • the pressure sensor outputs a voltage that is proportional to the applied pressure .... it requires all three pins ..... the interface board uses a 20mA current loop for data transmission .... the two are not directly compatible – jsotola May 21 at 22:06
  • @Max You might like to let us know your Arduino/Rpi experience, say do you know how to blink a LED, and how to use a multi-meter to measure voltage and current, do you know Ohm's law, voltage divider using 2 resistors in series etc, etc. Are you OK with Arduino C++, and/or Rpi python/node.JS? Or let us know your academic qualification such as a diploma or degree in EE etc. Then we can tailor our answers geared to you level of computer hardware/software knowledge and skills. – tlfong01 May 22 at 3:09
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Question

  1. Read 2 thermal couples and 1 pressure gauge using Rpi

  2. Record data and send it to server

  3. A better way to do this?

Answer

I skimmed the datasheet of your thermal sensor, pressure sensor, and current loop receiver module. My first impression is that they are all mission critical, industrial equipment.

Electrical characteristics of 3 pieces of equipment

  1. Thermal sensor: 4 thermal conducting wire, 4~20mA current loop

  2. Pressure sensor: power = 5V, signal output = 0.5V to 4.5V

  3. ADC module: INA196/ADS1115 based current/voltage ADC

Rpi to ADC module Interface Summary

  1. Communication protocol: I2C

  2. Programming languages (suggestion): python, C/C++, NodeJs, NodeRed

Advice / Warning to Rpi I2C ADC (INA196/ADS1115) newbies

I am new to building things like this and guess I just got confused. So for the pressure sensor I can just ignore one of the cables? Using the ground and signal cable. – Max 5

Well, your above comment worries me "a bit". During last couple of months I have been playing as an electronics/programming hobbyist, the hardware/software related to your project: current loop sensors including INA221, ADC including ADS1115, ...

The current sensor INA219 and voltage ADC 16 bit ADS1115 used in you project has a rather steep learning curve for newbies. You might like to first read the following posts on using these devices, to get a feeling of how hard it is. If you indeed found it scary, then I can recommend two simple devices ACS712 (current sensing and ADC combined, saving trouble for newbies) and PCF8591 (ADC, but 8 bit only). You can use these newbie friendly devices as a warm up exercise, before researching on you more advanced, industrial grade equipment.

Reading Voltage Input on ADC [using ACS712 and INA221]

Raspberry Pi Current & Voltage Sensors [using INA219/INA226, ACS712, ADS1015/ADS1115, ADS1256/AD7190]

/ to continue, ...

References

Dual Element Thermocouple probe with Standard Size Connector

Specifications

Two Sensor Readings Allows Two Readings of a Single Point

Continuous Monitor and Control & Built-in Backup

Analog Pressure Sensor

Specification

Typical Supply Voltage: 5VDC

Output Voltage Range: 0.5 – 4.5VDC

3-Channel 4-20 mA Current Loop Receiver 16-Bit ADS1115 I2C Mini Module

Features

3 Channel 4-20 mA Current Loop Receiver

3-Channel Input with 16-Bit Resolution

4-20mA Industrial Sensor Monitoring

INA196 Current Shunt Monitoring

Ideal for Sensor and Instrument Monitoring

ADS1115 16-Bit Analog to Digital Converter

Onboard 16V Voltage Supply (Boosted from 5V)

Ideal for Industrial Automation 4-20mA input

  • I am confused. I think for 16 bit resolution, there is not much choice. ADS1115 seems best. And ADS1115 is only I2C. Or do you have other non I2C 16 bit ADC? – tlfong01 May 22 at 12:25
  • Ah, the OP's combination is mission critical, industrial grade, or even military grade. The thermal couple used is also very expensive things. For long distances, current loop is good, because less noise, I think. I think those industrial experts knows three times more than me hobbyists, doing Mickey Mouse projects. So I don't dare to comment on the sensors. I only contribute humble comments on Rpi and ADC, because I did spend some time on them. – tlfong01 May 22 at 12:28
  • Perhaps you are right. Actually I am just making wild guesses. I only know the thermal sensor and pressure sensor are 10 times more expensive than I can afford. – tlfong01 May 22 at 12:53
  • This is in a industrial application. I am a computer engineer who does the software kind of things way more than the industrial. I would consider myself a newbie, because this is a lot different than my software expertise. Thank you for the help, price really doesn't matter about $1,000 per device would be fine. Just trying to find a cheap alternative. – Max May 22 at 13:09
  • @Max Ah, Rpi is indeed cheap, but I think it is ideal/appropriate for R&D rapid prototyping/feasibility study. In the mean time, you can also explore industrial grade Rpi, such as CM3, or customized Rpi4 by E14, say, element14.com/community/docs/DOC-76955/l/…. And actually ads1115 is not that ideal for industrial applications. A better alternative is ASD1256, 24 bit resolution, and more NOISE FREE - raspberrypi.stackexchange.com/questions/95843/… – tlfong01 May 23 at 3:13

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