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Sensor Input Conditioning

R

Richard

Jan 1, 1970
0
I have to build a terminal board which will accept

0-5 vdc
1-5 vdc
0-20 ma
4-20 ma
RTD

all jumper selectable. Each channel will have 3 terminals, Grd, 12 vdc, and
Signal. The ADC input is for 0-5 volts. I have all the voltages and
milliamp ranges figured out with jumpering a 250 ohm precision resistor to
ground for milliamp.

How does one convert a RTD signal to voltage? I've tried to search but I'm
coming up with more sales then tech info.

Thanks,
Richard
 
J

Jasen Betts

Jan 1, 1970
0
I have to build a terminal board which will accept

0-5 vdc
1-5 vdc
0-20 ma
4-20 ma
RTD

all jumper selectable. Each channel will have 3 terminals, Grd, 12 vdc, and
Signal. The ADC input is for 0-5 volts. I have all the voltages and
milliamp ranges figured out with jumpering a 250 ohm precision resistor to
ground for milliamp.

How does one convert a RTD signal to voltage? I've tried to search but I'm
coming up with more sales then tech info.

feed it with a constant (or predictable) current and measure the voltage
across it. use a small current to avoid heating the device.

a large resistor to +12V would be a good start.
 
J

Jamie

Jan 1, 1970
0
Richard said:
I have to build a terminal board which will accept

0-5 vdc
1-5 vdc
0-20 ma
4-20 ma
RTD

all jumper selectable. Each channel will have 3 terminals, Grd, 12 vdc, and
Signal. The ADC input is for 0-5 volts. I have all the voltages and
milliamp ranges figured out with jumpering a 250 ohm precision resistor to
ground for milliamp.

How does one convert a RTD signal to voltage? I've tried to search but I'm
coming up with more sales then tech info.

Thanks,
Richard
RTD's are resister devices.
you have a set ohm value at a set temp.
it simply is a resister changing it's value with
temp..
off the top of my head i can think of one that is 100 Ohms
in spec.
many devices use a current limiting source in series with
a calibration with a RTD to supply a 4..20 ma current input.
 
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