TEC Source Arroyo 5235, User Manual

5235 

TECSource

 User’s Manual · Page 21 

To manually adjust the PID, start by changing the I and D values to zero, and 

adjust the P value so that it reaches the set point as quickly as possible without 
overshooting the set point an unacceptable amount. Gradually increase the I 
value until the set point is achieved without oscillation. In many systems, the D 
term is not needed and may be left at zero. 
 
For additional information on PID loop tuning, consult online resources such as 

Wikipedia (http://en.wikipedia.org/wiki/PID_controller) or search for terms such 
as “Ziegler-Nichols method”, or “PID Loop”. 
 

Compensating for Cable Resistance 

 
Because the high currents the 

TECSource

 can drive through the Peltier, the 

voltage loss through the cable and connectors of the system can significantly 
affect the TEC voltage measurement. In most cases, accurate voltage 

measurements are not needed, and the default compensation of the instrument 
is sufficient. To improve the compensation, the 

Cable R

 setting in the menu 

allows you to specify the cable resistance, which is then used to dynamically 
subtract the voltage drop by simply using the formula V = IR to calculate the 
voltage loss, where I is the TEC ITE current, and R is the 

Cable R

 setting. This 

value is then removed from the voltage measurement to display an accurate 
TEC voltage measurement.  
 
The safest method of calculating cable resistance is to short the ITE+ and ITE– 
connections, making sure whatever you are using to short the terminals is not 

itself adding resistance to the circuit. Use short, heavy gauge wires, preferably 
soldered onto the terminals to minimize any resistance the short might add. 
Place the short as close to the Peltier as is reasonable. A simple approach is to 
unplug the cable from the mount and place a shorting plug on the mount end of 
the cable, which is easily made from a male DB15 connector and a soldering 

iron to solder the ITE+ and ITE– pins together. Make sure the Peltier is 
disconnected to protect it from current overloading during the test. 
 
Change the instrument to ITE mode and set the current to 5A. Depending on 
your setup, you may first need to change the Mount to User Defined and adjust 
the limit to 5A. Turn on the output and after the voltage has stabilize, make a 

note of it and turn the output off. Enter the measured voltage into the following 
equation to calculate 

Cable R

: 

Cable R = Voltage / 5 

Enter the resulting values into the 

Cable R

 menu entry and return the instrument 

to its original configuration. Typical values for 

Cable R

 are 0.008 to 0.040, but 

depend on your actual configuration.