Practical Instrument Electronics 334Plus - Manual (Page 9)

Practical Instrument Electronics
82 East Main Street Suite 3.14 • Webster, NY 14580 Tel: 585.872.9350 • Fax: 585.872.2638 • [email protected] • www.piecal.com
Page 9
OUT OF RANGE SIGNALS
Signals below 0 mA or open circuits are indicated
by 0.000 mA (-25.00%) on the display. Signals
above 52 mA are current limited by protection
circuitry to approximately 54 mA.
KEEPING THE PROCESS GOING
When an instrument in a critical control loop
develops a problem it is important to maintain
control of the process. The PIECAL 334Plus can
be substituted for a faulty controller or transmitter
to provide temporary manual control of the
process. One technician takes manual control of
the process while a second technician retrieves,
installs and configures a replacement instrument.
OPEN LOOPS
The display will indicate ERROR and 0.000 mA
or -25.00% if there is an open loop or if the
polarity is reversed. Check all the connections in
the loop or try reversing the leads.
POWER TRANSMITTER
Adjusting the SOURCE output to full scale (>24
mA) supplies a nominal 24V DC to power a 2
Wire Transmitter while simultaneously displaying
the 4 to 20 mA output of the transmitter.
READ MILLIAMPS
Select READ milliamps by moving slide switch
q to “mA” or “% 4 to 20mA” and moving slide
switch w to “READ”. Place the PIECAL 334Plus
in the loop in series with the current to be
measured.
SOURCE MILLIAMPS or 2-WIRE SIMULATOR
Select “SOURCE” using slide switch w to output
from 0.000 to 24.000 milliamps using the
PIECAL 334Plus’s internal power source. This
will provide 24V DC. Select “2-WIRE” to control
the current in a loop that is using an existing
power supply.
To change the output current adjust the dial
knob
r . Turning clockwise will increase the
output value, turning counter-clockwise will
decrease the output value with 0.001 mA
(0.01%) resolution. Press and turn the knob for
faster dialing with 0.100 mA (1.00%) resolution.
The output is adjustable in all EZ-CHECK™
positions.
When returning to the “4.00mA”/“0.0%” and
“20.00mA”/”100%” positions they will always
return to 4.00 (0.0%) and 20.00 (100.0%) mA.
This method is superior to keypad units. The
zero and full scale positions can be adjusted
smoothly making easy valve end stop testing,
trip point testing, alarm testing, etc. There is
virtually no overshoot/undershoot simplifying
testing.
READ DC VOLTS
Select “READ VDC” using slide switch
q to read
volts DC. Clip the leads across the voltage to be
measured.
GROUND LEAK DETECTION - when ON the
334Plus has the ability to check for current leaks
caused by ground faults, moisture or corrosion
that bypasses the current control element or
transmitter. The 334Plus powers up the 2-wire
transmitter or loop and indicates the total current
and the uncontrolled current. This provides
information useful in troubleshooting loop errors.
Application Notes