Dear Sir´s I have the following situation:
I need to connect a passive sensor from STS sensors model TM/N, link below
https://www.stssensors.com/Pressure...tName=NiveausondenTM_N&vId=0#NiveausondenTM_N

This sensor have an output of 0-25 mV and a power supply of 15V.
I need to connect this sensor to a logget from Inventia model MT713, link below
http://www.inventia.pl/ENG/MT-713_b...er_and_data_logger_with_GPRS_transmission.htm
This loggers can power the sensor without problem wuth 15V the issue is the signal input as the logger hava an analog input range
from 0-5V.

So my question is can I use a kind of istrumentation amplifier to be connect such sensor to this logger?
Can any one help me in the development of an electric circuit to made this connection and have a good resolution?

With best regards

David

MOD: Added d/s clips.E

 

Hi David,
Something like an INA326:
http://www.ti.com/lit/ds/sbos222d/sbos222d.pdf

makes a very simple option for such an application. The gain is easily to program with a minimum of components, and the data sheet is very helpful.
You may be able to find similar ones with a larger power supply range that would allow you to drive it directly from your sensor power supply however.

 

A broad compendium / reference for IAs that may help -

https://www.analog.com/media/en/tra.../designers-guide-instrument-amps-complete.pdf


Regards, Dana.

 

What power sources are available to run the interface circuit?

How accurate does the output need to be down around 0 V?

ak

 

The INA122 will work on a single supply up to 36 volts, minimum output offset is 100mv .
This can be eliminated with additional circuitry if needed.
SG

 

Hi David,
Something like an INA326:
http://www.ti.com/lit/ds/sbos222d/sbos222d.pdf

makes a very simple option for such an application. The gain is easily to program with a minimum of components, and the data sheet is very helpful.
You may be able to find similar ones with a larger power supply range that would allow you to drive it directly from your sensor power supply however.

Thank you I think this can solve my problem.
As I can see I need to have a gain of 100.
My only issue is that I have an signal of 0-25 mV if I have an signal of 0-50 mV with a gain of 100 I will have an output of 0-5V that is wath i need

 

A broad compendium / reference for IAs that may help -

https://www.analog.com/media/en/tra.../designers-guide-instrument-amps-complete.pdf


Regards, Dana.

Thank you
David

 

What power sources are available to run the interface circuit?

How accurate does the output need to be down around 0 V?

ak

Hi I have 5V, 15V and 24V for power sources.
At zero I must have 0 mV output

 

My only issue is that I have an signal of 0-25 mV if I have an signal of 0-50 mV with a gain of 100 I will have an output of 0-5V that is wath i need

Thats no problem! See page 9 on the data sheet, it tells you how to get any gain you want!

 

At zero I must have 0 mV output

That could be a problem. "Rail-to-rail" devices and circuits cannot actually produce an output voltage exactly at either rail. To get an output at exactly 0 V, you generally need a circuit that can swing below 0 V at least a little bit. There are tricks to get around this for AC signals such as audio, but not for slowly-varying DC signals.

Since you are not making much output current, one solution is a small charge-pump circuit to generate a small negative voltage to power the opamps.

ak

 

Thats no problem! See page 9 on the data sheet, it tells you how to get any gain you want!

Yes thank you. With a 0 to 25mV signal I need a gain of 200, so i will use R2=100 Ohm and R1=1 Ohm and will get the gain that i need.
I will buy this amplifien and make same test and will give feedback. Thank you for the fast and usefull help.

Regards,
David

 

i will use R2=100 Ohm and R1=1 Ohm and will get the gain that i need.

No, you won't.

Read the datasheet. The tables on page 9 list the recommended values for a gain of 200.

ak

 

I still think the INA122 is a better choice with its larger supply range.
SG

 

No, you won't.

Read the datasheet. The tables on page 9 list the recommended values for a gain of 200.

ak

Yes you are rigth must be R1=2kOhm and R2=200kOhm.
Thanks