# Multifunction DAQ

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## How to read pressure in real units (e.g bar) from input analogue voltage?

Hi

I have 35 X HTT Pressure Transmitter (3 wires) and NI-9205 which acquires the reading of the pressure sensor 35 X HTT as voltage. How can I convert it to bar for example?

Thanks

Message 1 of 8
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## Re: How to read pressure in real units (e.g bar) from input analogue voltage?

According to this data sheet, the sensor has a range of 0 to 1 Bar and an output voltage range of 0 to 10V.  This makes the math easy: just divide by 10.

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Message 2 of 8
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## Re: How to read pressure in real units (e.g bar) from input analogue voltage?

So, Is it always a linear relationship? If my sensor ranges 0 to 30 bar, first divided by 10 then multiply by 30?

Thanks

Message 3 of 8
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## Re: How to read pressure in real units (e.g bar) from input analogue voltage?

@alhabeeb wrote:

So, Is it always a linear relationship? If my sensor ranges 0 to 30 bar, first divided by 10 then multiply by 30?

Thanks

Unless told otherwise in a datasheet, assume linear relationship.  Because the min of both the voltage and measurement, it is a simple 30Bar/10V = 3Bar/V.

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Message 4 of 8
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## Re: How to read pressure in real units (e.g bar) from input analogue voltage?

In the datasheet:

But I didn't understand it.

Message 5 of 8
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## Re: How to read pressure in real units (e.g bar) from input analogue voltage?

@alhabeeb wrote:

In the datasheet:

But I didn't understand it.

These are about the internal working of the transmitter and do not care in the context of the electrical equivalents.

Treat the output signal as linear mapping to the pressure measurement range.

Santhosh
Soliton Technologies

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Message 6 of 8
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## Re: How to read pressure in real units (e.g bar) from input analogue voltage?

As you said, I should have 0.333333 (V) when I measure the ambient pressure, Should I?

I'm using ni-9205 to aquaire the out signal. I connected pin 1 and pin 3 to negative and positive, respectively to the power supply 23 (V), and I connected pin 2 to channale 0 of the ni-9205 and the negative terminal from the power supply to COM of the ni-9205 and I used differential configuration, but I got not logic voltage readings (e.g. -0.4)!

Any suggestion to solve this issue?

The photos of my devices are shown here

Thanks

Message 7 of 8
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## Re: How to read pressure in real units (e.g bar) from input analogue voltage?

@alhabeeb wrote:

As you said, I should have 0.333333 (V) when I measure the ambient pressure, Should I?

I'm using ni-9205 to aquaire the out signal. I connected pin 1 and pin 3 to negative and positive, respectively to the power supply 23 (V), and I connected pin 2 to channale 0 of the ni-9205 and the negative terminal from the power supply to COM of the ni-9205 and I used differential configuration, but I got not logic voltage readings (e.g. -0.4)!

Any suggestion to solve this issue?

The photos of my devices are shown here

Thanks

Approximately 0.33V for 1 bar pressure.

Were you able to confirm the sensor outputs 0.33V using a multimeter?