Yamatake Corporation Installation
ST3000 Smart Transmitter Series 900 Electronic Differential Pressure/Pressure Transmitter 4-31
Power supply and load resistance
• The load resistance of the intrinsically safe circuit and the supply voltage
must be determined in such a way that the following formula holds:
R: Loop resistance (Ω)
Vz: Voltage drop of Approved Zener Barrier
• Load resistance is the sum of the resistance that is connected to the output
terminals of the equipment such as the resistance of the cable loop and
the internal resistance of the connected instruments.
Lightning protection
When your transmitter is equipped with optional lightning protection, you must con-
nect a wire form the transmitter to ground as shown in Figure 4-22 to make the protec-
tion effective.
Figure 4-22 Ground Connection for Lightning Protection
Conduit seal
For an explosion proof installation in Class 1,Division 1, Group A locations only, you
must seal the conduit entrances in the electronics housing. However, you can skip the
conduit seal requirement for installations in Groups B,C, and D locations.
If a seal is required, use a conduit seal on the wiring outlet of the housing or junction
box.
WARNING
In explosive atmospheres and non-intrinsically safe loops, do not apply power to the
transmitter with the electronics housing end-cap removed, and do not remove the end-
cap with power applied to the transmitter.
Install the conduit seal according to the instructions packaged with the product.
250 R Supply voltage⋅ 10.8–()0.0218⁄≤≤
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