RKI Instruments GD-K77D - Manual (Page 13)

Model GD-K77D Operator’s Manual Description • 8
CAUTION: When the Model GD-K77D is not used for long periods of time, the lithium battery may lose
power. The lithium battery, under normal operating conditions, has a life expectancy of about
three (3) years from the date of manufacturing. When the lithium battery is replaced, put the unit
into maintenance mode before replacing the battery by pressing the Mode switch for 3 seconds.
Then calibrate the unit as described in the Calibration section. If the Model GD-K77D has been
stored for a long time, calibrate the Model GD-K77D when the unit is put back into service.
Sensor (17). Detects the target gas.
Detector Unit Set Screw (18). Tighten this screw when attaching the wall mounting
bracket to the Model GD-K77D’s case.
Terminals (19). Provides terminations for external wiring.
Flowmeter (20). The flowmeter indicates whether the sample flow rate of the sample
reaching the sensor inside the Model GD-K77D is okay. See “Flowmeter” for more
information.
Block Diagrams
Figure 4: Electrical Block Diagram
Pum p
Low flow sensor
GD-K77 D 4-20 m A
Transmis sion
Trans mis sion
Co ntrol unit
(MO DE) (FL OW ADJ.s t ) TEST/SET)
Pum p
Amp unit Sens or
Pow er source
POWE R INPU T(24 VDC )
Alarm con tac t control
Dis play
Gas alarm co ntac t
(ALM 1, ALM 2)
Troub le alarm co ntact
(Trouble)
- Relays are normally
de-energized (N DE)
- Contacts close at
alarm condition
(PW /TR) (ALM 1) (ALM2 ) (SKIP)