Pressure is the next most important parameter
after Temperature. In Hydraulics and Pneumatics,
the measurement, indication, control and
logging-charting of pressure is indispensable.
Popular Pressure Sensors are based on either
Piezoresistive or Strain-Gauge Technologies.
Strain-Gauge types can be Metal Foil or
The Analog Strip Chart Recorder is used in
Simple Systems where a Record or Report has to
be generated. Data Loggers and PC based Data
Acquisition Systems expand this capability by
making the Data Electronically Accessible for
Charting-Analysis and Reporting using database
Advanced Sensor Technology
The Liquid-Fluid Level in containers of uniform
cross-section can be computed by measuring the
pressure of the fluid head. In cases where
levels of semi-volatile fluids are measured,
sensors with Micro-watts of power usage or data
transmission is required to protect from
sparking related accidents. Even Zener Barriers
can help reduce risks due to wrong connections
or cross connection due to cable damages.
In the field, due to various constrains many
safety practices can be overlooked or
circumvented. The Sensors and System design must
be over-engineered in some cases to safeguard
Ensure Flow Sensor Output 4-20mA is properly
connected to the Flow Controller polarity reversal
will show reducing reading in the Display as Flow
rises. The Motor / Drive used and Power selected
must be able to bring the Flow more than the
maximum required Flow rate directly without
control (open loop).So when in doubt connect
motor/drive and run at max power and observe
maximum flow rate e. g. if max. flow obtained with
Motor at 100% Power (direct) is 300 lph the
STC1000PFC can control flow rates upto 260 lph.
Keep PB in middle position and power on system
e.g. set Flow rate to 200 lph. Now Observe
maximum overshoot. and adjust proportional band as
in table. (PB Control is a 300 lph Single Turn
Control with Ends.) SP 200 lph, PV (Process
After each change turn on system again to see
response till 2 % or less variation or overshoot
or oscillations are obtained.
If proportional band setting is maximum, fully
clockwise turn till end (single turn pot) the
motor will slowly ramp up to full flow speed and
ramp down slowly to reduce flow.
If proportional band is at the minimum, the motor
will go full speed till it comes close to the set
flow rate and turn off abruptly almost like an on
/ off controller the motor may pulsate on &
off near setpoint.
There is an additional control called Reset or
Error Cal EC ( Integral) which is factory set for
SP=PV 50% Power Output i.e. Output Control = 12mA.
In certain cases after stable reading is obtained
after adjusting or tuning PB the Flow may
stabilize say at 195 lph for a set point of 200
lph the process is stable but a ten lphrees
process error is present. this can be Corrected
with EC or RESET POT at the rear panel (this is a
endless 10 Turn Pot).
Adjust Error Cal provided in the back panel to
increase Flow rate to 200 lph from 190 lph. when
this is done give some time for system to respond
after every 1/2 a turn 180 lph of the RESET (EC)
control pot .
The RESET control is a Ten turn potentiometer
like the SP potentiometer after 10 turns the
direction of turning must change. Clockwise
Increases Flow rate Anticlockwise decreases Flow
rate. (at min. PB setting EC pot sets the On / Off
or Operating Point).