4/20mA Sensorsignal to a 0-10V Signal

[christinescoms]

Hi all

i need to convert a 4/20mA Sensor signal
to a 0-10V Signal
load cell transmitter
Are there simple schematics for this?

thanks
diegor747

 

[danadak]

Plenty of circuits in the datasheets in application section -

https://www.ti.com/amplifier-circuit/special-function/4-20ma-signal-conditioners/overview.html

https://www.ti.com/lit/ug/tiduam6/tiduam6.pdf?ts=1658312420174&ref_url=https%253A%252F%252Fduckduckgo.com%252F

https://e2e.ti.com/blogs_/b/analogwire/posts/4-20-ma-industrial-loops-made-easy

The basics of 4-20mA current loop transmitters - Planet Analog

The most common type of 4-20 mA transmitter is the 2-wire topology, or a 2-wire sensor transmitter

www.planetanalog.com

Regards, Dana.

 

[Ian Rogers]

A simple resistor if you can manage with a small DC offset

A 500 ohm resistor generates 10v at 20mA but 2v at 4mA

So 2~10v from 4mA~20mA or do you need 0v..

 

[Ian Rogers]

A 680 ohm generates 0~12 so a difference amp set to 2v puts it right..

But remember if your circuit runs on 12v you won't get 12v, the 4~20mA loop would need to run at 24V

 

[crutschow]

Below is the LTspice simulation of a one opamp circuit to convert the 4-20mA to 0-10V:
It uses a CMOS rail-rail type op amp.
It has a 100 ohm resistor (R3) to generate a 0.4V to 2V signal (green trace) from the sensor current, to minimize the voltage required from the sensor.
This is amplified with a gain of +6.25 by the op amp while removing the offset to get the 0-10V signal (yellow trace).

 

[Chrisnia]

Great thread. I am installing sensors on a marine engine and have been looking far and wide for the best 0-5 v or 4-20 ma temperature probe that is very compact, can handle 0-150 C and withstand engine room temperatures. There was an AD22100 based screw in temp sensor but it ran on 5vdc. The boat runs a 12 vdc system. I do not want to have to use a voltage converter in the engine room. Any ideas regarding the best threaded (NPT) small form factor sensor that can run on 12 DC and output a 4-20 ma or 1- 5 V ? I ffel like I am looking for a pink unicorn. It must be very accurate and reliable . I can map the output so calibration is not an issue.

 

[crutschow]

The boat runs a 12 vdc system. I do not want to have to use a voltage converter in the engine room.

If you can't find a 12V sensor, then consider putting a simple 12V to 5V regulator (i.e. LM317 or LM7805) at the signal receiver end, and running an additional wire along with the sensor wire from there to the engine room for the 5V.

 

[Chrisnia]

Thanks for the input; the receive is mounted on the engine and the converter would be subject to temps up to 85C. Just out of curiosity why is it so hard to find a ma or v output on an precision 12 volt powered temp sensor.

 

[crutschow]

the receive is mounted on the engine

What does the receiver do with the information?

why is it so hard to find a ma or v output on an precision 12 volt powered temp sensor.

I haven't really looked into that, so can't give you a learned answer.

 

[Chrisnia]

The "receiver" is a J1939 10 channel analogue to CAN encoder. Very robust and programmable.

 

[crutschow]

Deleted

 

[rjenkinsgb]

why is it so hard to find a ma or v output on an precision 12 volt powered temp sensor.

The LM35 series sensors would appear to be perfect for the job.

Some versions are rated to operate from -55 to +150'C. With a single positive supply the reading range is 2 - 150'C.
With a negative bias resistor added to the output they will work in the below zero range as well.

They will work with either a 5V or 12V supply.

https://www.ti.com/lit/ds/symlink/lm35.pdf

https://www.digikey.co.uk/en/products/filter/temperature-sensors-analog-and-digital-output/518?s=N4IgjCBcoLQExVAYygFwE4FcCmAaEA9lANogCsIAugL7X4KSkAyAsgMwWX4BsiIAlgBMoIGGAAMEfAAdUIkPlQBPadhEBDAM4paQA

I'd use screened cable to connect them to minimise noise pickup.

 

[Chrisnia]

Thank you for the very detailed response. LM35 is definitely the correct module ; however I need it in an enclosed sensor (NPT) to install into the application on the engine. I would not even know where to start to put this sensor into the appropraite form factor. Any ideas regarding a prepacked sensor ready to install?

Thanks again for your efforts

 

[rjenkinsgb]

Exactly what thread and style fitting do you need - and what quantities, either total or eg. per month?

 

[Pommie]

There's also the DS18B20 sensor which comes in a sealed variety. However, it's a one wire device so needs some programming to read and it's 5V only but can be parasitically powered - it depends how programmable your "receiver" is. The LM35 is probably going to be easier to connect to.

Mike.

 

[christinescoms]

The LM35 series sensors would appear to be perfect for the job.

Some versions are rated to operate from -55 to +150'C. With a single positive supply the reading range is 2 - 150'C.
With a negative bias resistor added to the output they will work in the below zero range as well.

They will work with either a 5V or 12V supply.

https://www.ti.com/lit/ds/symlink/lm35.pdf

https://www.digikey.co.uk/en/products/filter/temperature-sensors-analog-and-digital-output/518?s=N4IgjCBcoLQExVAYygFwE4FcCmAaEA9lANogCsIAugL7X4KSkAyAsgMwWX4BsiIAlgBMoIGGAAMEfAAdUIkPlQBPadhEBDAM4paQA

concrete polishing cape coral
I'd use screened cable to connect them to minimise noise pickup.

also thank you for your help

 

[Chrisnia]

Exactly what thread and style fitting do you need - and what quantities, either total or eg. per month?

Hello,
We only need 4 units. I still do not understand why it is so hard to find.

THanks

 

[crutschow]

We only need 4 units. I still do not understand why it is so hard to find.

It would help if you can answer the question about what size thread fitting you need for the sensor.

 

[christinescoms]

@Chrisnia thank you so much for your suggestion

 

[Reloadron]

Any ideas regarding the best threaded (NPT) small form factor sensor that can run on 12 DC and output a 4-20 ma or 1- 5 V ?

Yes, I have plenty of ideas. Since you mention NPT fittings I will assume you are looking at engine temperatures such as coolant? My choice for a sensor based on your applications would likely be Type K thermocouples with a stainless steel sheath material. Choose the length and diameter based on your needs. Next based on the sheath diameter you use a compression coupling which are very common and come in about any NPT size you want. Anyway for NPT you want to use a compression fitting. Just as an example when considering sheath material for a sensor since you mention a marine application if you are sensing coolant temperature if the coolant is for example sea water you want a sheath resistant to salt water unless you are on the Great Lakes where salt corrosion is not a problem. A Google of Thermocouple and RTD compression fittings will more than get you started. All you need to know is your sheath diameter and NPT pipe diameter.

Since you already have apparently a 4 to 20 mA loop I am guessing you already have your sensor choice done.

Any ideas regarding the best threaded (NPT) small form factor sensor that can run on 12 DC and output a 4-20 ma or 1- 5 V ?

The reason you see numbers like 4-20 mA, 1-5 volts and 2-10 volts is those are popular industry standards but also require a 24 VDC supply which you don't have. Again my choice of sensor would be a thermocouple. Next you need a transducer which just means a way to get from what you have to what you want. A Google of thermocouple amplifier will bring up a dozen small boards for thermocouple amplification which run on 5 VDC and give an amplified output proportional to temperature. You run off your thermocouple using thermocouple extension wire. You get your 5 VDC using a common buck converter. You already have your A/D.

This is merely how I would approach things as to monitoring engine parameters as to temperatures. If you want pictures or links to anything I have suggested just ask.

i need to convert a 4/20mA Sensor signal
to a 0-10V Signal

Now if that's all done I would as suggested just use a 500 ohm 1% resistor in your 4 - 20 mA current loop which gives you 2 - 10 volts and program your CAN J1939 for an analog 2 - 10 VDC analog in and scale it to your temperature range for your dashboard display. Accuracy is a qualitive term and means little less being defined.

I have tried to keep this all modular using off the shelf modules in an effort to make things simple and easy. There is no shortage of published schematics out there if you choose to roll your own.

Ron