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38 Micro Motion
®
Model 1700 and 2700 Transmitters
Output Wiring – Model 1700/2700 Intrinsically Safe Transmitters
Hazardous area voltage
The Model 1700 or 2700 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.
Hazardous area current
The Model 1700 or 2700 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.
Hazardous area capacitance
The capacitance (Ci) of the Model 1700 or 2700 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
Hazardous area inductance
The inductance (Li) of the Model 1700 or 2700 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
WARNING
A transmitter that has been improperly wired or installed in a hazardous area
could cause an explosion.
To reduce the risk of an explosion:
• Make sure the transmitter is wired to meet or exceed local code requirements.
• Install the transmitter in an environment that complies with the classification tag
on the transmitter. See Appendix A.
Table 5-2 Safety parameters
Value
Parameter 4–20 mA output Frequency/discrete output
Voltage (U
i
) 30 V 30 V
Current (I
i
) 300 mA 100 mA
Power (P
i
) 1.0 W 0.75 W
Capacitance (C
i
) 0.0005 μF 0.0005 μF
Inductance (L
i
) 0.0 mH 0.0 mH