The 3175 RTD Resistor Kit includes four pieces of 1.00 KiloOhm resistors. These precision resistors were used to interface Platinum RTDs to the 1046 – PhidgetBridge . This configuration has been obsoleted by the TMP1200  RTD Phidget, which can interface with RTDs without the need for external resistors. If you still need precision resistors, you can find them at electronic component suppliers such as DigiKey.
Platinum RTDs (Resistive Thermal Devices) are used to make very precise temperature measurements. RTDs are very accurate, and will measure temperatures up to 500 degrees Celsius. The electrical resistance of the RTD changes predictably with temperature, and RTDs are the most accurate commonly available temperature sensors.
Measuring the resistance of an RTD requires accurate components all through the system  otherwise there is no point in paying for an RTD. The resistors in the 3175 RTD Resistor Kit have a worst case error of 0.1%  translating to a typical temperature error of 0.05 Celsius. The resistors also change their resistance very little with temperature  ambient temperature variation is a significant source of error for thermocouples. RTDs with a well designed data acquisition system will not be subject to these temperature variation errors.
Read the RTD Interface Kit user guide to get detailed instructions on how to construct and test the bridge.
Resistor  

Resistance Value  1 kΩ 
Resistance Error Max  0.1 % 
Customs Information  
Canadian HS Export Code  8533.10.00 
American HTS Import Code  8533.10.00.60 
Country of Origin  US (United States) 
Go to this device's product page 
The 3175 RTD Resistor Kit includes four pieces of 1.00 KiloOhm resistors. These precision resistors are used to interface Platinum RTDs to the 1046 PhidgetBridge. Platinum RTDs (Resistive Thermal Devices) are used to make very precise temperature measurements. RTDs are very accurate, and will measure temperatures up to 500 degrees Celsius. The electrical resistance of the RTD changes predictably with temperature, and RTDs are the most accurate commonly available temperature sensors. Measuring the resistance of an RTD requires accurate components all through the system  otherwise there is no point in paying for an RTD. The resistors in the 3175 RTD Resistor Kit have a worst case error of 0.1%  translating to a typical temperature error of 0.05 Celsius. The resistors also change their resistance very little with temperature  ambient temperature variation is a significant source of error for thermocouples. RTDs with a well designed data acquisition system will not be subject to these temperature variation errors. Wiring the resistors to your RTD allows the 1046 PhidgetBridge to convert the resistances into a voltage, which it then measures. The PhidgetBridge is by far the most precise Phidget device for measuring voltage. The PhidgetBridge also cancels the errors resulting from USB voltage variation. 
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.
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:
Where is the Bridge Value given by the PhidgetBridge (in mV/V) , and and are the resistances of the known resistors.
In order to get the highest accuracy from the RTD, consider the following:
The PhidgetBridge Bridgefull application will allow you to verify that your PhidgetBridge is working, and that your wiring is functional. Please check the 1046 User Guide for instructions on launching the application. The PhidgetBridge has the ability to amplify the measured signal  it was built to measure extremely small signals. Amplification is not necessary with RTDs, so we recommend leaving the gain set to 1 unless you want higher precision at low temperatures at the cost of saturating before it reaches higher temperatures. If amplifier is in danger of saturating (reaching the limit), an Overrange error will be thrown. When using the Bridgefull application, remember to check the Enabled box, to power up the bridge and start measurements.
There are several standards for RTDs. Common RTDs are built from platinum, the most common models being Pt100 and Pt1000. The 100 or 1000 refers to the resistance of the RTD and 0 Celsius. We have calculated formulas for the PT100 and PT1000 standards to convert the Bridge Value in (mv/V) directly into a temperature.
Some RTDs are not standardized, so we cannot provide a formula to convert the Bridge Value to temperature. The following formula will calculate the resistance of the RTD or thermistor from the bridge voltage  a good start for computing the temperature. To calculate temperature, check the manufacturer’s data sheet for formulas or tables for converting resistance to temperature.
By passing current through the RTD, it will heat up, distorting your temperature measurement. To determine the power dissipated as heat in the RTD use the following formula,
The RTD manufacturer will often specify the temperature increase of the RTD as a function of power (watts). This
power was calculated in the previous equation. This temperature increase will depend on if it is attached to a larger object that will sink the heat away, or if there is air movement over the RTD. A simple way to reduce the effects of selfheating is to enable the bridge in software during the measurement period, and disable the bridge until the next measurement.
Using these resistors in a circuit with an RTD or another resistive sensor allows it to be accurately read by wheatstone bridge interfaces. See the User Guide of the Bridge Interface for detail on how to build the circuit.
Product  Board Properties  

Part Number  Price  Controlled By  Number of Bridge Inputs  Data Rate Max 
PhidgetBridge 4Input

$90.00  USB (MiniUSB)  4  125 Hz 
PhidgetBridge 4Input

$95.00  USB (MiniUSB)  4  — 
Wheatstone Bridge Phidget

$30.00  VINT  2  50 Hz 
Here's a list of RTDs we have available: