Yamatake Corporation Installation
ST3000 Smart Transmitter Series 900 Electronic Differential Pressure/Pressure Transmitter 4-23
Grounding
If a shielded cable is used, earth (ground) the shield at the receiver only (single point
ground). Connecting the shield to signal ground is recommended to make the electric
potential difference lower.
If the transmitter is not grounded through a pipe stanchion, ground the transmitter
using an earth terminal in the transmitter.
To ground the transmitter, the ground resistance must be 100Ω or lower.
Supply power and external load resistance
Confirm the relationship between the external load resistance and the supply voltage.
As shown in the illustration, the relationship should be inside the shaded area.
External resistance: the total resistance connected to the output terminals of a transmit-
ter (includes resistances of all cables in the loop plus the internal resistance of the
instruments).
The horizontal axis represents the supply voltage of a transmitter, and vertical axis
represents the external load resistance
.
Figure 4-18 Supply Voltage and External Load Resistance - Relationship
~Note 1: 45 volt operation is permitted.
~Note 2: For communication with SFC, a load resistance of 250 ohms or more
is needed.
0 16.3 2410.8
250
605
45.0
1560
@
Supply voltage (V DC)
Load resistance (Ω)
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