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XTR106: Vref and Vreg voltage is zero in XTR106

Prodigy 235 points

Amir Poursadegh

Replies: 21

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Part Number: XTR106

I have to design a 4-20 mA transmitter circuit for a load cell with 520ohm impedance.

I used XTR106 and circuit that mentioned in figure 5 of XTR106 datasheet.

but i don't have any Vref voltag for supplying my sensor means the voltage is zero so my current is zero too. (Vreg is zero too)

my circuit is:

I don't know what is the problem. maybe the the XTR106 was damaged but all 5 ICs that i bought had a same result.

I would be thankful if someone could help me...

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kai klaas69
- Mar 3, 2019 12:11 PM
Hi Amir,

why do you have a GND connection at the bridge? Take care, don't connect anything of the XTR106 circuit to GND!

Kai
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Prodigy 235 points

Amir Poursadegh
- Mar 3, 2019 12:24 PM
In reply to kai klaas69:

my sensor has a wire for shield....
what would be happened if i connect GND to my XTR106 circuit ?...I'm sure it would be ok if I connect pin7 to GND for example
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kai klaas69
- Mar 3, 2019 12:31 PM
In reply to Amir Poursadegh:

Hi Amir,

the whole XTR106 circuit is floating and the voltage at pin 6 is shifted by the voltage drop of output current across burden resistance (the load resistance which is connected from pin 3 to pin 2 of connector P1). So, you must not connect pin 7 or any other pin of XTR106 to GND!

And it's not wise to use GND as a shield for the bridge either. Connect the shield to pin 6 instead. But take care that pin 6 is not connected to any foreign potential!

Kai
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Prodigy 235 points

Amir Poursadegh
- Mar 3, 2019 12:41 PM
In reply to kai klaas69:

Hi Kai
thanks for your helpful answers... I will correct my circuit
but my question is why I don't have Vref voltage? is it related to Vref and Vreg voltage?
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kai klaas69
- Mar 3, 2019 1:24 PM
In reply to Amir Poursadegh:

Hi Amir,

I don't know. Eventually, the XTR106 was destroyed by unintentionally connecting GND to the XTR106?

I would correct the circuit and check it with a fresh XTR106.

Kai
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Amir Poursadegh
- Mar 4, 2019 9:37 AM
In reply to kai klaas69:

How I could be sure that XTR106 was destroyed or not? is it a check test for it?
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kai klaas69
- Mar 4, 2019 12:18 PM
In reply to Amir Poursadegh:

Hi Amir,

if your circuit is correct and the XTR106 is ok, then the circuit should work. If not, then there might be an error left in the circuit or the XTR106 might be damaged.

The schematic you have shown, is it complete or are there any extensions using GND? What is the purpose of the "Span" signal at pin 1 of P1?

Kai
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Prodigy 235 points

Amir Poursadegh
- Mar 4, 2019 12:46 PM
In reply to kai klaas69:

Hi Kai

It's not complete I have another part for cut the circuit and give constant current...but I test this circuit alone without another thing and results was same (i didn't use sheild pin as you mentioned)...are you sure if I connect GND to pin 7 of XTR106 (with a mosfet), the XTR106 would be damaged?
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kai klaas69
- Mar 4, 2019 12:51 PM
In reply to Amir Poursadegh:

Hi Amir,

can you show the schematic with the MOSFET?

Kai
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Prodigy 235 points

Amir Poursadegh
- Mar 5, 2019 5:52 AM
In reply to kai klaas69:

Hi Kai

this is the whole of my circuit

AD694 do it's duty well but XTR106 is not.
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