Bridge questions

Any hardware type questions or problems for all other Phidget devices.
EddyQ
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Bridge questions

Postby EddyQ » Thu Mar 28, 2019 1:38 pm

I'm considering DAC1500 or 1046 Bridge for measuring temperatures with RTDs. I'm a little confused with the guides.
https://www.phidgets.com/docs/1046_User ... idge_Input

1) I assume what is referred as bridge voltage (Vb) is the voltage that is on the 5V terminal. And this terminal is an output of the USB input voltage and the ADC reference. Is this true?

2) For computing range, if Vb=5V and Gain=1, I apply +2.5V to V-, the full scale range of voltages on V+ would be 0 to +5V correct? Note: I'm not sure this is possible without upsetting maximum input levels of ground+0.25V and 5V-0.25V.

3) For computing range, if Vb=5V and Gain=2, I apply +2.5V to V-, the full scale range of voltages on V+ would be +1.25 to +3.75V correct? Basically gain only applies to differential voltage between V+ & V- pins and not common mode voltage to ground.

4) Max bridge current spec is 50mA. I assume that means the current out of 5V connection.

All voltages relative to ground connection.

jdecoux
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Re: Bridge questions

Postby jdecoux » Mon Apr 01, 2019 10:25 am

The Voltage Ranges for all gain settings for a particular bridge input are listed in the Technical Details section of the User Guide for that device.

1046 Gain Specifications
DAQ1500 Gain Specifications

The 5V terminal is the reference voltage, and is derived from USB 5V.
The 50mA current spec for the DAQ1500 is for current from the 5V terminal.

If you are measuring RTDs, you may also want to consider the TMP1200 RTD Phidget


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