Thermo Scientific 3403 Manual page 50

Section 8
Appendices
8-18 Midi 40 CO2 Incubator
Table 7-6. O2 Sensor Pin Out
TP13 - "TC" Tank Switcher Status & Voltages
Tank 1 Tank 2
(CO2 Primary) (CO2 Backup)
Empty
Empty
Empty
Empty
Empty
Empty
Empty
Empty
Empty Empty
Empty Empty
Empty Empty
Empty Empty
The tank switcher circuit is a simple circuit comprised of pressure switches
in parallel with resistors. These in turn are connected in a serial fashion to
a voltage supply. With the presence of gas pressure, the associated switch
closes and shorts out the corresponding resistors. This results in different
voltage levels at TP13 (A/D channel 6 input). The table above outlines
the 16 possible scenarios along with the expected voltage level at TP13.
The simplest manner to troubleshoot the tank switcher circuit is to
disconnect it at the CPU and enter the 'Plug N Play' Mode. Turning the
unit off and powering it up while pressing the up arrow enters PNP mode.
Then scroll to the tank set up screen – this screen is updated in real time –
no delays. Shorting between the following pins on the CPU board should
result in a full indication (F) for the corresponding tank. Note that pin 1
is closest to the component designator label (J21 or J22).
J22 pin 1 to 2 T3
J22 pin 3 to 4 T4
J21 pin 1 to 2 T1
J21 pin 3 to 4 T2
Tank 3 Tank 4
(O2/N2 Primary) (O2/N2 Backup) (VDC)
Empty
Empty
Empty Empty
Empty
Empty
Empty Empty
Empty
Empty
Empty Empty
Empty
Empty
Empty Empty
Ideal Voltage
0.000
1.716
1.447
2.347
0.962
2.117
1.922
2.595
2.243
2.776
2.676
3.041
2.513
2.938
2.857
3.159
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