Thermo Scientific 3403 Manual page 46

Section 8
Appendices
8-14 Midi 40 CO2 Incubator
TP1 "LM335-1"
Only used for units with a TC CO2 Sensor. TC CO2 application
requires the use of two A/D channels and the differential is used for
CO2 calculation. TP1, A/D channel 0, is referred to as V
cally the voltage produced by a precision voltage divider. Typically, this
will measure approximately 2.4 VDC under normal operation. With
nothing attached to this location, 0 VDC should be present. If the TC
board and sensor are in circuit and greater than 5 VDC is measured here
(i.e. approximately 5.4 VDC), the sensor or interconnectivity should be
suspect. Under this condition, "Err" will be displayed at the front of the
unit. An easy way to demonstrate this condition is to disconnect the TC
sensor, at the sensor or at JP3 on the 192040 board. The table below
covers some additional TC fault conditions.
Table 7-4. Additional TC Fault Conditions
Condition
Sensor - no connection
J1 - bad connection
J2 - bad connection
JP4 - bad connection
TP7 "LM335-2"
TP7, A/D channel 1, is referred to as Vm- and is the actual voltage pro-
duced by the TC Sensor. The sensor is comprised of two thermistors.
One is sealed – only influenced by temperature; one is open – influenced
by temperature as well as other environmental factors. In simple terms,
Vm- is the voltage produced by another resistive voltage divider. Under
normal operation the voltage at TP7 will fluctuate in the ~2.4 VDC
range. Refer to TP1 for addition observations on TP7.
TP9 "LM335-3"
All applications – humidity channel. In proper operation, TP9 will be in
the range of 1.0 to approximately 3.9 VDC. If no sensor is connected, 0
VDC will be present at TP9. Pressing all three buttons (increment,
mute/mode, and decrement) can access the current RH reading. This
value, the voltage at TP9, and the current temperature (offset removed),
should correlate via the following expressions:
V [TP9] = V
OUT SUPPLY
RH) + 0.16)
Sensor RH = (-1.919E-09*V
- 21.75) / (1 + (T - 23)*2.4E-03)
RH = Sensor RH/(1.0546 – 0.00216T), T in °C
TEMP. COMP.
RH is ultimately the value to be displayed. If the values correlate
TEMP. COMP.
TP1
~5.4 VDC
0
~2.4 VDC
0
(0.0062 (Sensor RH) + 0.16) = 5 (0.0062 (Sensor
3 + 1.335E-05*V
OUT
[V
OUT
+ and is basi-
m
TP7
Toggles 0 & ~5.4 VDC
~2.4 VDC
0
0
2 + 9.607E-03*V
OUT
in mV, RH in %, T in °C]
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