3.13
.
3.3.4 Sample Flow Sensor Input
If the sampling system supplying the process sample to the 2500 is fitted with a loss of
flow sensor, this can be connected to the 2500 to enable the "loss of sample flow"
diagnostic to operate, which in turn triggers the analyser's Fault alarm. See Figure 3.1.
2500 Power Control PCB 02500911A
Loss of flow diagnostic triggered by contact closure between: TB36 – 1 and TB36 – 2.
3.3.5 Solenoid Valve Drives
Autocalibration routines are provided as standard on the 2500, and if they are to be
used, suitable 3-way solenoid valves can be plumbed into the sampling system as
shown in Fig 3.5. Two or three valves may be used and all should be located
conveniently close to the 2500. Each valve is switched via the 2500 Power Control PCB
relays as illustrated. The valves are selected for operation by the 2500 as shown in
Table 3.4 and Table 3.5. Connect the valves to the appropriate terminals using suitable
screened cables and glands, and attach screens to the nearest earth stud with the
minimum length of screen. See Figure 3.1.
The Autocalibration relay contacts are rated at 240VAC/1.0A, 30VDC/1.0A. The
contacts are fitted with an R-C snubber (100R + 47nF) to provide transient protection
when used with AC solenoids. 220/240Vac solenoid valves with a power rating less
than about 6VA are not recommended because the 'leakage' current through the
snubber may prevent low power solenoids from de-energising correctly.
Solenoid valves may use an external power source, or the internal 24VDC/12VA power
source may be used. When using the internal power source, ensure that the 12VA
rating is not exceeded. DC solenoid valves must have built-in suppression diodes fitted
across the coil to protect the relay contacts.
WARNING
If the Keyswitch is left "ON" (contacts closed), access is continuously
available to all normally protected areas of the software.
NOTE
In common with all fault diagnostics this alarm will only be cleared by restoration of
flow/opening of contacts.
WARNING
Where the 2500 analyser is in a hazardous area, suitable protection concepts
must be used to connect the loss of flow sensor to the 2500 analyser.
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