7835
Hydrazine Monitor
9 Maintenance
26
IM/7835–EN Rev. P
Sensor assembly
Referring to Fig. 9.2, page 25:
1. Replace the platinum anode.
2. Holding the white closure cap tightly in place on the filling
syringe, snap the syringe plunger into position and remove
the white closure cap.
3. Place the blue Luer fitting on the syringe nozzle.
4. Slowly inject the filling gel through the bottom filling hole in
the outer jacket of the sensor until it reaches the top vent
hole.
5. Remove the syringe and replace its closure cap.
6. Push the sensor into the clips on the sub-panel – the clips
incorporate small protrusions that cover the filling and exit
holes in the outer jacket.
7. Connect the tube from the mixing coil to the bottom of the
sensor.
8. Plug the red and blue sensor connectors into their
respective colored sockets on the liquid handling panel.
9.4.6 Simple Electronic Check
In the unlikely event that a problem is encountered with the
monitor, use a current (µA) source and a resistance box to test
the transmitter.
A Sensor Simulator is available to make an overall check on the
functioning of the transmitter unit.
The simulator, that connects to the analog board, produces a
current output to emulate the hydrazine sensor signal and also
provides the necessary resistance to simulate Pt1000 values.
Refer to the simulator manual for full details of its use, or
connect a current source plus a resistance box to the
transmitter.
To perform a simulated calibration proceed as follows:
1. Open the sensor unit door and locate the electrical
connection box mounted on the door (see Fig. 4.6, page
11).
2. Open the connection box and disconnect the sensor and
thermistor connections as follows:
31:
+ve Sensor (R)
32 :
– ve Sensor (B)
33: Pt1000
(Y)
35 :
Pt1000 (Bk)
3. Connect the appropriate wires of the current source and
resistance box to TB2 as follows:
current ve:
31
current source -ve:
32
Resistance box:
33
Resistance box:
35
4. Set the appropriate resistance value corresponding to the
thermistor resistance at the nominal sample temperature,
for example:
20 °C = 1077.9
Ω
5. Select the nominal calibration value to 80 µg kg
-1
.
6. Set the current source to 25 µA.
7. Initiate a calibration sequence by pressing the CAL button.
8. After 15 minutes the display reads the selected
concentration value.
9. Check the monitor range with different µA values. The
relative values are as follows:
µA
µg kg
-1
3.125
9.1
6.250
19.2
12.500
39.5
18.750
59.7
25.000
80.0
31.250
100.3
Warning.
The gel contains silver oxide and sodium
hydroxide. It is caustic and stains skin and clothing.
Note.
Take care to hold the sensor firmly at the top so
that the centre portion is not pushed out when the
tube is connected
Note.
The monitor calibration signals are established by
read-only software and cannot be changed by users.
Note.
When the electronic systems are operating correctly,
the displayed concentration value should be within
± 0.2 µg kg
-1
of the selected value.
