Emerson MICRO MOTION 1700 - Manual (Page 92)

Safety parameters (continued) Table 8-1:
Parameter 4–20 mA Frequency/discrete
Capacitance (C
i
) 0.0005 μF 0.0005 μF
Inductance (L
i
) 0.0 mH 0.0 mH
Voltage The transmitter’s safety parameters require the selected barrier’s open-
circuit voltage to be limited to less than 30 VDC (Vmax = 30 VDC). This
voltage is the combination of the maximum safety barrier voltage
(typically 28 VDC) plus an additional 2 VDC for HART communications
when communicating in the hazardous area.
Current The transmitter’s safety parameters require the selected barrier’s short-
circuit currents to sum to less than 300 mA (Imax = 300 mA) for the
milliamp outputs and 100 mA (Imax = 100 mA) for the frequency/discrete
output.
Capacitance The capacitance (Ci) of the transmitter is 0.0005 μF. This value added to
the wire capacitance (Ccable) must be lower than the maximum allowable
capacitance (Ca) specified by the I.S. barrier. Use the following equation to
calculate the maximum length of the cable between the transmitter and
the barrier: Ci + Ccable
≤ Ca
Inductance The inductance (Li) of the transmitter is 0.0 mH. This value plus the field
wiring inductance (Lcable), must be lower than the maximum allowable
inductance (La) specified by the I.S. barrier. The following equation can
then be used to calculate the maximum cable length between the
transmitter and the barrier: Li + Lcable
≤ La
I/O wiring for Model 1700 and Model 2700 transmitters with intrinsically safe outputs
88 Micro Motion ® Model 1700 and 2700