AI 4-20 mA HART CHARM specifications

Installation notes

This CHARM requires a CHARM Terminal Block.
This CHARM supports 2-, 3-, and 4-wire devices.
Support for 3-wire devices requires either the CHARM 3-Wire AI Fused Injected Power Terminal Block, or the CHARM Terminal Block and the 24 VDC Power CHARM.
In 3-wire and 4-wire configurations, removing the AI 4-20 mA HART CHARM from its terminal block does not disconnect field power from connected devices. In order to disconnect field power from connected 3-wire and 4-wire devices, you must either remove the fuse from the CHARM 3-Wire AI Fused Injected Power Terminal Block or remove the 24 VDC Power CHARM from its terminal block.
Emerson recommends 4-wire over 3-wire configurations because 4-wire configurations are less susceptible to noise.
If you are using the 24 VDC Power CHARM for 3-wire or 4-wire devices, refer to the 24 VDC Power CHARM specifications for information about wiring and removing field power.

Table: AI 4-20 mA HART CHARM specifications
Item	Specification
Channel type and functionality	Analog input: 4-20 mA 0-20 mA 4-20 mA with HART
Nominal signal range (span)	4-20 mA 0-20 mA optional
Full signal range	0-24 mA
Input impedance	250 Ω ±1%
2-wire transmitter power	15.0 V minimum at 20 mA with 24 VDC input power. Current limited to 30 mA maximum.
Accuracy over temperature range	0.1% of span (0 to 60°C) 0.25% of span (-40-70°C)
Repeatability	0.05% of span
Resolution	16-bit
Calibration	None required
Input power requirements	Total power requirement: +24 VDC ±10% at 36 mA maximum for 2-wire configurations and 12 mA maximum for 4-wire configurations: Input power from CIOC: +6.3 VDC ±3% at 32 mA maximum +24 VDC input power: +24 VDC ±10% at 25 mA maximum
CHARM heat dissipation	0.33 W
HART scan time	Typically less than one second but is dependent on HART communication loading and the capability of the HART device.
HART Communications	HART 7 pass-through request/response HART 7 variable report Field device status report

Figure: AI 4-20 mA HART CHARM wiring diagram for 2-wire applications

Figure: AI 4-20 mA HART CHARM wiring diagram for 3-wire applications

Figure: AI 4-20 mA HART CHARM wiring diagram for 4-wire applications