Data Sheet

1/6/2018 1046 User Guide - Phidgets Support
https://www.phidgets.com/docs/1046_User_Guide#Measuring_Resistive_Thermal_Devices_.28RTD.29 7/9
This diagram shows how to connect the RTD to a Wheatstone bridge,
and then to a PhidgetBridge 4-Input.
Each bridge input can be powered down, reducing power consumption with 1046 sensors, and useful for reducing
heating of sensors, which can introduce errors.
Changing the Data Rate
Using a slower sampling rate will reduce the noise in the measurements dramatically. The noise figures are specific
to individual applications and sensors. The lowest noise level achievable is 5nV/V RMS.
Measuring Resistive Thermal Devices (RTD)
Using a Wheatstone Bridge
A Wheatstone bridge is the classic method of
measuring unknown resistances, and requires
three resistors of known values. It uses the
current in each leg of the bridge to create a
voltage differential between both voltage
dividers. Using the voltage differential and the
three known resistors, the resistance of the
fourth resistor can be determined.
To determine the resistance of the RTD, the
following formula can be used:
Where is the Bridge Value given by the PhidgetBridge (in mV/V) , and , and are the resistances of
the known resistors.
Using a Voltage Divider
The alternate method requires only two resistors. This reduces the amount of error that can be introduced into the
system due to resistor tolerances. A voltage is applied to the two resistors and the RTD in series. The voltage drop
across the RTD is measured. Using the voltage drop and the values of the two resistors, the resistance of the RTD
can be determined.
To determine the resistance of the RTD, the following formula can be used: