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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
Troubleshooting RTD Instruments
When you are having an issue where an
instrument won't read an RTD sensor or you
don't know if the calibrator is connected properly
the PIE 311Plus has a function to measure and
display the fixed or pulsed sensor (excitation)
current that the instrument uses to measure the
resistance of the RTD sensor.
Double click the
e
DIAL KNOB at any time the
unit is on and then turn the
e
DIAL KNOB to
move to the second menu page so the word
DISPLAY
appears at the top of the menu.
Turn the
e
DIAL KNOB to move through the
menu until the cursor is pointing at SENSOR
mA. Press the
e
DIAL KNOB to toggle SENSOR
mA ON.
Disconnect all sensor wires from the devices to be
calibrated and connect the PIE 311Plus to the
inputs of the device using 2, 3 or 4 wires. The sensor
current generated by the instrument will be indicated
on the display followed by the word FIXED or
PULSE. Older single channel RTD instruments used
a constant (fixed) current source to measure an RTD
sensor. Smart transmitters, multichannel recorders
and PLC or DCS input cards switch the current
source sequentially through the channels which is
seen as an intermittent (pulsed) current.
Instrument with RTD Input
Controller
Temperature Transmitter
Temperature Indicator
Temperature Trip or Alarm
Pt 100
α
=3850
01.15mA PULSE
289.27 Ω
°C
3 2 1 4
100.0
OFF
OVERLOAD
Double Click
Menu
HI
SET
LO
SOURCE
MAX
READ
MIN
READ
Push & Hold
to
Store/Step
Push & Turn
for
Fast Dialing
Diagnostic RTD &
Milliamp Calibrator
2, 3, 4 Wire Detection
Loop Leak Detect ∙ Transmitter Supply
+
-
-
+
°C
00.21mA FIXED
289.27 Ω
525.00
01.15mA PULSE
289.27 Ω
525.00
°C
Troubleshooting RTD Instruments
Excitation current generated
by the RTD Instrument
Excitation current generated
by the RTD Instrument