Wavelength Electronics WTC32ND, Datasheet And Operating Manual

Page: 21 / 37

© 2022 www.teamWavelength.com 21
WTC32ND TEMPERATURE CONTROLLER
OPERATING WITH THERMISTOR TEMPERATURE SENSORS
A thermistor sensor has the best sensitivity, very small size, a temperature
range of -80º to +150º C, but poor linearity.
Thermistor temperature sensors should connect one terminal as close
as possible to GND (Pin 13) to avoid parasitic resistances and voltages
affecting temperature stability and accuracy.
The diagrams on this page demonstrate how to configure the WTC32ND
for operation with a thermistor temperature sensor. An online calculation
utility to determine resistances is available at:
www.teamwavelength.com/support/design-tools/wtc-calculator/ .
Figure 16. Thermistor / TEC Operation -- Top View
Figure 17. Thermistor / Resistive Heater Operation -- Top View
IF YOU ARE UPGRADING FROM THE WHY SERIES: The position of Pin 1 on the WHY is reversed (or mirrored) relative
to the position of Pin 1 on the WTC32ND.
V
S
V
DD
TIE GROUND CONNECTIONS DIRECTLY TO PIN 13
1
WTC32ND
Temperature
Controller
1
2
3
4
5
6
7
14
13
12
11
10
9
8
Actual
Temperature
Monitor voltage
V
DD
R
T
R
BIAS
R
I
R
P
R
LIMA
R
LIMB
Adjusting PI
Control Loop
Adjusting Limit
Currents
V
SET
VSET = Sensor Resistance X Sensor Bias Current
1
1
-
+
TOP VIEW
NC
OR
D/A
V
DD
Bandgap
Voltage
Reference
W
CCW
OR
QUICK CONNECT LEGEND
DIAGRAM
REFERENCE
TABLE OR EQUATION
R
LIMA
Table 9 on page 25
R
LIMB
Table 9 on page 25
R
P
Table 11 on page 27
R
I
Table 12 on page 27
R
BIAS
Table 10 on page 26
Equation 6 & Equation 7
R
T
Thermistor datasheet
R
G
N/A
V
S
V
DD
TIE GROUND CONNECTIONS DIRECTLY TO PIN 13
1
WTC32ND
Temperature
Controller
1
2
3
4
5
6
7
14
13
12
11
10
9
8
Actual
Temperature
Monitor voltage
V
DD
R
T
R
BIAS
R
I
R
P
1.5 k
Ω
R
LIMB
Adjusting PI
Control Loop
Adjusting Limit
Currents
V
SET
VSET = Sensor Resistance X Sensor Bias Current
1
1
NC
V
S
TOP VIEW
NC
V
DD
Bandgap
Voltage
Reference
W
CCW
OR OR
D/A