Setting Safety Limits - ILX Lightwave LDT-5900 Series User Manual

R
T
T = Temperature in °C
The A, B, and C, are derived from resistance measurements at 0, 100 °C and
260 °C, and are defined as follows:
A =
B = (- * )/100
C
T<0
where:
where:
where:
For temperatures greater than 0 °C, the 5900 controller derives the temperature
by solving the following quadratic equation:
T = - R
-------------------------------------------------
00000000000002 R
These sensor coefficients (A, B, C and R
accurately report the temperature when utilizing an RTD sensor. Typical RTDs
have a nominal resistance (R
Common Callendar-Van Dusen constants are listed below and are used as default
values in the LDT-5900.
• A(
• B(
• C(
For optimal accuracy and stability, the 1mA current source should be selected for
RTD sensors with resistance of 1 to 6000 ohms. In general, the change in
resistance per change in temperature is much lower for a typical 100
that of a typical 10 k thermistor. The proportional and integral terms for the PID
loop must be increased appropriately when using an RTD sensor for optimal
setting time and stability.

Setting Safety Limits

TEC modules can be damaged by excessive current, and module manufacturers
typically specify a maximum safe operating current for their module. The LDT-
5900 provides a current limit feature that allows you to set the maximum current
01_10
= Resistance ( ) at temperature T (°C)
+ ( * )/100
2
4
= (- * ß)/100
= R - R / 100 * R
100 0
ß = Constant for T < 0 C
* (1 + * 260) - R
= R
0
2 2
A + (R A -4 R
w
0 0
B
0
o -1 -3
C ) = 3.908 x 10
o -2 -7
C ) = -5.775 x 10
o -4 -12
C ) = -4.183 x 10
Ba sic TEC Op era t ion Inst ruct ions
0
/ 4.16 * R
260 0
B(R - R ) )
0 0 T
) are required for the LDT-5900 to
0
) of 100 or 1000 ohms.
0
O P E R A T I O N S
*
LDT-5980/ 5948
2
C H A P T E R
RTD than
37