technical NOTES

h. The calibration of the transmitter is only possible under off line conditions
using a suitable tool kit.
i. The performance of the transmitter is not affected by aging factor. Hence, it
tenders longer good reliability and better repeatability unless calibration is
disturbed.
j. Availability of transmitter is possible either from manufacturer or from
authorized dealers only and delivery takes more than three months from
date of order.
k. Transmit ters are useful in process control application where accuracy matters.
l. Cabling: Interfaced with DCS through Profibus cable in daisy chain fashion
and hence Cables from Transmitters to DCS are reduced compared to normal
analog transmitters. This reduces cost marginally.
m. Cable Erection: Faster erection of cables is possible and thus commissioning
time is reduced.
n. Ease of Calibration and Maintenance: Re-ranging and other parameters can
be changed through the remote terminal at CCR which saves the time of
maintenance & calibration.
o. Fault Diagnostics: Since the transmitters can be accessed at engineering
station at CCR, the instrumentation engineer can do the complete fault
diagnostics, in case of faults and hence reduces the downtime.
p. I/O Hardware reduction: Since Analog IO modules are not required; the
space required at IO panels is less which results in reductions of panel cost.

7. 2 Tech n ic a l Co m pa riso n

Technical Comparision Of Process Parameter Measurement Devices

S.N. Description Mechanical Switches Analog Trans-mitter TransmitterSmart TransmitterProfibus

1 Type of output Contact ( NO

or NC)

Analog , 4-20

mA

Analog ,4-

20mA with

HART

Digital

2 Accuracy + / - 1 to 2% + / - 0.1 to 0.5% + / - 0.01 to 5% + / - 0.075 to

0.01%

3 Reliability Good Excellent Excellent Excellent

4 Operation &

Maintenance

Ease

Good Very Good Excellent Excellent

5 Turn Down Ratio

for Measuring

Cell Span

Fixed or max.

10 , leads to

maintain more

inventory

Fixed or max.

10,leads to

maintain more

inventory

100 or more ,

hence requires

less no. of

inventory

100 or more

, hence

requires

less no. of

inventory