Michell Instruments Easidew Online, Руководство пользователя

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Easidew Online User’s Manual
Michell Instruments 25
OPERATION
3 OPERATION
As supplied, the instrument is ready for operation and has been set-up with a set of
default parameters. This section describes both the general operation of the instrument
and the method of setting it up and changing the default parameters should this become
necessary.
The default parameters are as follows:
• Span -100 to +20°Cdp (-148 to +68°Fdp) or 0 to 3000 ppm
V
• Temperature units °Cdp
• Current loop input, 4-20 mA (7.5°C/mA or 13.5°F/mA)
• Re-transmission current loop output, 4-20 mA (7.5°C/mA or 13.5°F/mA)
• Alarm 1 set-point -20°Cdp (-4°Fdp)
• Alarm 2 set-point -40°Cdp (-40°Fdp)
• Data communications, Unit address 1, Baud rate 9600, Parity None, Stop
bits 1
For the supplied dew-point transmitter, the span and current loop input setting should
not be changed. The span will require changing if the instrument is to be ranged in
°F, if a different transmitter is employed, if the user chooses to re-range the Easidew
transmitter or if ppm
V
is selected.
The instrument must also have been installed as detailed in Section 2 and connected to
a sample gas supply that is representative of the process being monitored.
3.1 General Operational Information
Operation of the Easidew Online is completely automatic and once set-up requires little
or no operator intervention.
The dew-point transmitter is designed to operate in a fl owing gas stream of between
1 and 5 Nl/min (2.1 and 10.6 scfh) when mounted in a sample block, at operating
pressures up to a maximum of 45 MPa (450 barg / 6500 psig). Direct pipeline mounting
requires 1 to 10m/sec (0 to 32.8fps) at pressures dependant on the type of material
used (customer de fi ned).
The sample gas is taken into the sample block via the Gas In port and, in fl owing
through the sample block, comes into contact with the dew-point transmitter which,
in turn, produces a current loop output signal proportional to the measured dew-point
temperature. This output signal is converted to a real time analog dew-point temperature
reading by the monitor.
If data logging is required, the monitor will need to be connected to a suitable host and
temperature readings extracted via the RS232 interface.
The gas fl ow through the sample block must be controlled outside the instrument,
typically by means of a needle valve located in the sample gas input line.