D-Guard
2
58
19.
APPENDIX B:
19.1.
Disabling the Display Backlight
By default, the display backlight is enabled for Group II versions of D-Guard
2
and disabled for Group I versions.
The backlight LEDs, when enabled create a voltage drop of around 3.0V in the power supply fed to the internal
electronics. For many applications, this is acceptable and no changes are necessary.
For applications where long cable lengths, large barrier resistances and low power supply voltages are present, it may
be required to disable the backlight LEDs to gain additional voltage compliance for the current loop output to function
up to 22mA.
Disabling the LEDs gives around 130 Ohms extra available loop resistance at 22mA, or will allow the supply voltage to
be operated 3.0V lower for a given loop resistance.
Determining whether the backlight link needs to be fitted requires an understanding of the characteristics of the
components of the system into which the detector is installed. If in doubt consult the system designer, plant engineer
or other body with knowledge of the system.
Place link here to disable backlight
DO NOT OPEN UP D-GUARD
2
IN A HAZARDOUS AREA.
WORK ON D-GUARD
2
MUST ONLY
BE CARRIED OUT IN A SAFE AREA.
Summary of Contents for D-Guard2
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Page 65: ...D Guard2 62 23 APPENDIX F 23 1 System Menu Map ...
Page 68: ...D Guard2 65 25 APPENDIX H Product Certificates 25 1 IECEx Product Certificate ...
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Page 72: ...D Guard2 69 25 2 ATEX Product Certificate ...
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Page 76: ...D Guard2 73 26 APPENDIX I Product Dimensions ...
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