RADIOMETER TCM3 - Page 37

TCM3 and TCM30 Service Manual 2. TCM3
Electrode Performance Check, Continued
pO, Zero Point These checks are carried out using the service program.
and Sensitivity Insert the electrode in the holder and select test mode step 10. Press the A key to
start electrode heating. Supply green call gas (20.9% O:) to the electrode holder.
Wait 10 minutes for the signal to stabilize and read the signal (which is displayed -
as 0.x xx.x where x xx.x is in mV).
Change the gas supply to the blue cal2 gas (0% O,) and read the electrode signal
after 10 minutes.
Zero point: Check that the relative zero point, calculated as the relationship
between the electrode signal for the blue gas and the green gas, is
less than 0.04. The relative zero point is calculated as follows (B is
the actual barometric pressure):
Vgas2*B
Zero point(rel.) =
point(rel.) = ast #760
Sensitivity: Check that Vgasi is between:
795* В 636*B
V (min) = d mV =
mV (min) 760 and mV (max) 760
corresponding to a sensitivity between 0.5 mV/mmHg and 4.0
mV/mmHg ?.
Please note that a too high sensitivity may be caused by silver
deposits on the platinum cathode. The sensitivity may be reduced
by remembraning and rubbing the electrode surface carefully with
the cleaning paper. Never use emery paper or similar!
The sensitivity is calculated as follows:
Vgasi _. Vgasi
S(mV / mmHg) = ——————— =
(mY Imig) O2 pressuregasl 830.209
1) Normally, the pO, sensitivity is expressed in pA/mmHg, but the system
converts the current to an equivalent voltage; 10 pA corresponds to 1 mV.
Continued on next page
Yanana 3 」 9-31