Wiring
Wiring the Optional ISIO Boards
J4 is an isolated 24 volt output with a zener barrier output. The results of calculating
the values were very similar to the MTL 787 barrier. The MTL document “Cable
Parameters and Permitted Combinations” was used to determine the C and L values
below.
– Vo = 28.35 V
– Io = 106 mA ≥ fuse rated for 63 mA
– Ohm = 270
– Co = 79 nf
– Lo = 2 mH
– L/R ratio (uH / ohms) = 56
– Po = 1.02 W
HART
®
Communications
The HART Communication protocol is supported over port J11, the 4–20 mA
current output with an optional ISIO board. Communication with the gauge takes
place through an Emerson Electric Co. field communicator, Model 275 or newer.
Refer to the Interface Operation Guide for the DensityPRO / DensityPRO+ with
HART Protocol.
The entity parameters for port J11with the HART option are as follows:
– Vmax = 35.25 V
– Imax = 200 mA
– Ci = 0 nf
– Li = 0
– Pmax = 0.81 W
To connect the HART wiring:
– Use shielded, twisted-pair cabling with the proper conductor size
– Ground at one point only
– Ensure a properly specified power supply
Figure 4-22. Optional ISIO Board J11, HART Communications
4-14 DensityPRO Installation Manual Thermo Scientific
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