P/N: 974153 |
Rev: 072016
|
ECO: 46503
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6.7 SPX TRANSMITTER FUNCTIONS VIA HART
Zero Trim (1,2,5,1,3,1)
Digital Correction to zero which affects the digital output. This differs from Lower
Sensor Trim in that zero trim is ONLY performed at zero pressure.
Lower Sensor Trim (1,2,5,1,3,2)
Digital Correction to zero which affects the digital output. This differs from Zero Trim in that Lower
Sensor Trim can be performed at pressures above zero.
Note: This must be performed before Upper Sensor Trim. Only perform this function with a known
calibrated pressure source.
Upper Sensor Trim (1,2,5,1,3,3)
Digital correction to Full Scale which affect digital output.
Note: Lower Sensor Trim must be performed before Upper Sensor Trim. Only perform this function with
a known calibrated pressure source.
Digital to Analog trim (1,2,5,1,2)
This is used to match the digital representation of the analog output with its actual analog loop current.
Note: This should only be performed with a known Calibrated Current (mA) meter.
Reranging
The SPX allows for the 4 mA and 20 mA points (LRV and URV respectively) to be adjusted so that output
resolution can be improved. A Re-range or “Turndown” ratio of 6:1 is possible. Accuracy specifications
remain dependent upon the Full Sensor Range without any turndown applied. Three methods of Re-
ranging the SPX Transmitter are outlined below.
Note: If pressure applied to the transmitter is not in the range of the 6:1 turndown ratio, the transmitter
will reject the Span attempt. This will be indicated by the output not adjusting to 20 mA after a few
attempts using the Span Actuator.
Reranging via Zero/Span Actuators
When HART Communication is not used, LRV and URV values are entered by applying zero pressure to
the SPX-T and “Rezeroing” by:
i.
Do not remove seal screw when the circuit is live in a hazardous area.
ii.
Remove zero pushbutton seal screw.
iii.
Using a 2mm or smaller Allen key, depress the pushbutton for a ½ second.
iv.
Release pushbutton for a ½ second.
v.
Depress the pushbutton again for a ½ second and release.
The LRV and URV have now been adjusted to zero the device without affecting the span.
After Rezeroing, it is possible to set the span by adjusting the URV with the span actuator. The span
actuator should never be used to adjust the URV without using the zero actuator to set the LRV first.
ATTENTION
