Practical Instrument Electronics 434 - Manual (Page 8)

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 8
The PIECAL 434 is supplying the loop
voltage. There is an control loop error. This
may be a transmitter (set for upscale burnout)
with a bad or missing sensor, or a short in the
loop. The PIECAL 434 is supplying the loop voltage.
A calibrated transmitter is limiting the loop
current to 12.00 mA. An additional 0.28 mA is
not controlled by the transmitter and is leaking
somewhere in the loop.
mA OUT, % OUT (Percent of 4 to 20 mA)
Find current leaks in loops caused by ground faults, moisture or corrosion. The 434 simultaneously
supplies power to a 2 Wire Transmitter (or loop with a transmitter) while displaying the 4 to 20 mA
output and the amount of current leaking in the loop.
1) Disconnect one or both input wires from
the device to be calibrated.
2) Select “mA” or “% 4 to 20mA” with slide
switch q .
3) Select “SOURCE” using slide switch w .
4) Turn the knob r clockwise several times
until full scale output (>24.000
mA/125.00%) The display will indicate
“PWR MEASURE” and “LEAKAGE:”
5) Connect the red source lead of the PIECAL
434 to the plus (+) input of the device and
the black source lead to the minus (-).
The PIECAL 434 supplies a nominal 24 volts
DC at 24 mA to the 2 Wire Transmitter or loop. The current passed by the transmitter will be
accurately displayed by the PIECAL 434 along with an indication of leakage current at the bottom of
the display. If there is an uncontrolled loop, a transmitter with upscale burnout and bad or missing
sensor or a short the display shows “iLOOP > 24mA”
Note: Many installed transmitters will normally indicate 0.01 to 0.10 mA leakage without significant
control problem. Unstable readings may indicate loose connections or the presence of moisture.
Using Ground Leak Detection
PWR MEASURE OUT
24.179
mA
i LOOP > 24mA
PWR MEASURE OUT
12.280
mA
LEAKAGE: 00.28mA
Enabling Ground Leak Detection
Double click the
r DIAL KNOB at any time the unit is on and the following display will appear for 30
seconds:
Turn the
r DIAL KNOB to move through the menu. Press the r DIAL KNOB to toggle between OFF
and ON or to change the steps setting. These settings are remembered even with the power off.
EXIT MENU - exits this menu immediately and saves any changes. Menu will automatically exit after
30 seconds of inactivity.
GROUND LEAK DETECTION - when ON the PIECAL 434 has the ability to check for current leaks
caused by ground faults, moisture or corrosion that bypass the current control element or transmitter.
Setting Up Ground Leak Detection
Typical Error Conditions
Typical
2-Wire
Transmitter
+ IN - REF +OUT- Transmitter Input
Sensor
Process Signal
Simulated Input
Power 2 Wire
Transmitters
Dial Output to
FULL SCALE to Power 2 Wire
Transmitters
DIAL
AUTOMATED DIAGNOSTIC CALIBRATOR
4-20 mA
Push & Hold to Store/Step
Push & Turn for Fast Dialing
Double Click for Options
VDC %mA
mA OFF
100%
0%
12.280
PWR MEASURE OUT
LEAKAGE: 00.28mA
mA
12.280
PROCESS
INDICATOR