RADIOMETER TCM3 - Page 36

2. TCM3
TCM3 and TCM30 Service Manual
Electrode Performance Check, Continued
Signal Range
Signal Stability
pCO, Response
Check
pCO, sensitivity
check
The electrode signal must be within the specified range, see below, within one
minute after the electrode has reached the preset temperature. If not, ERROR 2
will be flashing in the AUX display and an acoustic beep will be heard. For the
combined pO-/pCO, electrodes ERROR 2 will only be displayed if both
parameters are outside range. If only one is outside, its display will show “- - -”, ©
The signal range check is finished when pO, and pCO; values are displayed.
Monitor pO, range is: -4.0 * B* 0.209 to -0.5 * B * 0.209
(-636 to -79.5 mV, at B = 760 mmHg).
Monitor pCO, range is: 49+Vrto 200+Vr
where V,, = 0.0793 * T* In(pCO, cal / 38) , and
T is the absolute temperature (=318 during the test)
The electrode voltages may be viewed using the service program (step 0:10 for
pO, and step 0:11 for pCO;).
After heating and range check the stability is checked. The average drift must be
less or equal to 1% per minute within 15 minutes after the SIGNAL RANGE
CHECK. If the drift is greater, ERROR 3 will be flashing in the AUX display and
an acoustic beep will be heard. For the combined pO2/pCO, electrodes ERROR 3
will only be displayed if the stability check fails for both parameters. If only one
fails, its display will show “- - -”. The SIGNAL STABILITY CHECK is finished
when the green READY LED is activated and an acoustic double-beep is heard.
This is a check of the electrode’s ability to detect rapid changes in the CO;
concentration. Remove the electrode from the holder after calibration (READY)
and check that ERROR 4 is not displayed in the AUX display. This “crack” check
is normally only relevant for E5237 and E5277 with giass pCO, electrodes.
This check is carried out using the service program.
Insert the electrode in the holder and select test mode step 11. Press the A key to
start electrode heating. Supply green call gas to the electrode holder. Wait 10
minutes for the signal to stabilize and read the signal value in the pO./pCO,
displays (displayed as 0.x xx.x where x xx.x is in mV).
Change the gas supply to the blue cal2 gas (10% CO.) and read the electrode
signal after 10 minutes. Check that the signal difference between the “blue gas
signal” and the “green gas signal” is minimum 17.0 mV corresponding to a
minimum sensitivity of 90%.
The sensitivity is calculated as follows (V gas2 and V gas! are in mV):
(Vgas2-Vgasi)*100 — _ Vgas2-Vgasl
S(%) = =
27.243* (in CO2% gas2 — In CO2% gasi) 0.1888
Continued on next page