Wavelength Electronics WTC3293, Manual

Page: 5 / 13

© 2013
PAGE 5
WTC3293
www.teamwavelength.com
WTC3293-00400-I
CONFIGURING THE EVALUATION BOARD
STEP 2: ADJUST THE PROPORTIONAL GAIN AND INTEGRATOR TIME CONSTANT
NOTE: This step must be done without the WTC3243 installed to allow accurate resistance readings.
The Proportional Gain and Integrator Time Constant can be adjusted during operation, but resistance
readings will not match these tables with the WTC3243 installed.
Table 2 suggests starting points for Proportional Gain and Integrator Time Constant depending on
your sensor type. To optimize control, refer to
Optimizing Thermoelectric Control Systems,
Tech Note
TN-TC01 ( http://www.teamwavelength.com/downloads/notes/tn-tc01.pdf#page=1 ).
Table 2 - Proportional Gain and Integrator Time Constant Trimpot Con fi guration
Sensor Type
Thermistor
100

Platinum RTD
P Gain
[A/V]
I Time Constant
[Seconds]
10
50 3
1
LM335
AD590 (Attach a 10 k

resistor across
and Sensor -)
2
2
25
25
I GAIN Trimpot
Resistance
21.4 k Ω
120 k Ω
35.9 k Ω
35.9 k Ω
PGain Trimpot
Resistance
11.1 k Ω
100 k Ω
33.3 k Ω
33.3 k Ω
PROPORTIONAL GAIN
Without the WTC3243 installed, use an
ohmmeter to measure resistance between test
points 5 and 6 (TP5 & TP6).
Adjust the PGAIN trimpot to the desired
resistance.
P is in A / V.
R
P
is in ohms.
An online design calculator is available to
assist in determining resistance values.
http://www.teamwavelength.com/support/cal-
culator/wtc/default.php
INTEGRATOR TIME CONSTANT
Without the WTC3243 installed, use an
ohmmeter to measure resistance between test
points 6 & 7 (TP6 & TP7).
Adjust the I TERM trimpot to the desired
resistance.
I
TC
is in seconds.
R
I
is in ohms.
An online design calculator is available to
assist in determining resistance values.
http://www.teamwavelength.com/support/cal-
culator/wtc/default.php
Equation 1
Calculating Rp from P
Equation 2
Calculating P From R
P
R
P
=
(
100,000
)
100 - 1
P
>Ÿ@
P =
(
100
)
100,000 + 1
R
P
[A / V]
Equation 3
Calculating R
I
from I
TC
Equation 4
Calculating I
TC
from R
I
R
I
=
(
100,000
)
(1.89) I
TC
- 1
>Ÿ@
I
TC
= (0.53)
(
100,000
+ 1
)
[Sec]
R
I