DI 24 VDC low-side sense (dry contact) CHARM specifications

Installation notes

This CHARM requires a CHARM Terminal Block.
This CHARM can be configured as a pulse count input channel.
Debounce filters can be configured for this CHARM in DeltaV Explorer.
This CHARM can sense relay/switch contact closure and supports line fault detection for detecting open or short circuits in field wiring when external line fault resistors are used. To use line fault detection you must:
- Enable line fault detection in the configuration.
- Connect the dry contact to a 12 kΩ resistor in parallel for open circuit detection and a 2.4 kΩ resistor in series for short circuit detection.

Figure: External line fault resistors

Table: DI 24 VDC low-side sense (dry contact) CHARM specifications
Item	Specification
Channel type	Discrete input: +24 VDC dry contact On/Off detection on the - (minus) signal
Detection level for On	<5.3 kΩ (>2.25 mA at 24 VDC)
Detection level for Off	>8.2 kΩ (<1.75 mA at 24 VDC)
Channel impedance	4.8 kΩ
Wetting voltage	22.5 VDC (±5%); current limited to 12.5 mA nominal
Open line fault detection levels	Guaranteed short circuit: < 100 Ω Guaranteed good status: 400 Ω to 40 kΩ Guaranteed open circuit: 75 kΩ
Optional pulse count input frequency range	0.1 Hz to 10 kHz with 50 µsec minimum pulse width
Input power requirements	Total power requirement: +24 VDC ±10% at 22 mA maximum : Input power from CIOC: +6.3 VDC ±3% at 32 mA maximum +24 VDC input power: +24 VDC ±10% at 10 mA maximum
CHARM heat dissipation	0.33 W

Figure: DI 24 VDC low-side sense (dry contact) CHARM wiring diagram