Adjust K Factor:
If the optional display is present, the K factor used in velocity
measurements may be adjusted. This is done by activating the K factor
adjustment function of the unit. To activate the K factor adjustment
function, take the shorting jumper from programming block PJ5 and
place it on the upper two terminals next to the letter “K”. See Fig. 5. The
display will now show the programmed pitot tube K factor. The K factor
can be adjusted up and down by using the zero and span buttons as up
and down buttons. Once the desired K factor has been set, replace the
shorting jumper on PJ5 to its velocity position (“V”). The shorting jumper
must not be left in the “K” position for proper operation of the unit. The
factory setting for the K factor is 1.0 and it is adjustable from 0.5 to 3.
Adjust Filter Time Constant:
If the optional display is present, the dampening filter time constant of the
output may be adjusted from 0.5 to 15 seconds in 1-second increments.
In turbulent air, the pressure reading may be unstable. The dampening
filter time constant is provided to reduce such noise. The time constant
is the actual filter time constant, not averaging time. For an abrupt
change in pressure it will take three time constants to reach 95% of the
final value.
To activate the filter adjustment function, take the shorting jumper for
programming block PJ3 and place it on the upper two terminals next to
the letter “F”. See Fig. 5. The display will now show the filter time
constant. The time constant can be adjusted up and down by using the
zero and span buttons as up and down buttons. Once the desired time
constant has been set, replace the shorting jumper on PJ3 to its original
position. The shorting jumper must not be left in the “F” position for
proper operation of the unit. The factory setting for the time constant of
the filter is 0.5 seconds.
USER CALIBRATION
The transmitter may be user calibrated. With the two buttons marked
“Zero” and “Span” (see Fig. 5) four calibration coefficients may be
altered: pressure zero, pressure span can be calibrated with the two
buttons marked “zero” and “span” (see Fig. 5). Analog output zero, either
0 V or 4 mA, and analog output full scale, either 5 V, 10 V or 20 mA may
be adjusted with two buttons marked “zero” and “span” in conjunction
with jumper settings. Pressure and output are calibrated separately to
ensure the displayed pressure is correct and the analog output has
accurately calibrated end points. These calibration coefficients are stored
in nonvolatile memory, which retains its content indefinitely without
external power or batteries. Factory calibration may be easily restored.
To calibrate the transmitter you will need three pieces of equipment.
First, you will need a calibrated pressure source capable of generating a
stable pressure value for the maximum range of the unit under test. You
will need a manometer or gage capable of validating the calibration
pressure unless that is built into the pressure source. You will also need
a voltmeter or milliammeter to calibrate the output. The transmitter is
calibrated using the following procedure.
Preparation – Depending upon if it is a 2-wire or 3-wire system, connect
the voltmeter or milliammeter and power supply, being careful to observe
polarities. The transmitter must be calibrated in a vertical position. Make
sure the unit has been returned to its factory default span and zero
settings by pressing and holding both the “Zero” and “Span” switches,
simultaneously, for about 4 to 5 seconds (doing this can be necessary to
erase bad zero and span values that might have been stored by a
previous user of the Magnesense
®
unit).
Calibrating Pressure Zero – Leaving the hose barbs vented, press and
hold the “Zero” switch for about 4 to 5 seconds. The zero point should
now be set and, if the display is present, the display will read zero.
Calibrating pressure should begin with setting the zero first, then the
span, since the zero setpoint will affect the span value. Once the “Zero”
is set, for uni-directional models, your output reading should be close to
4.0 mA or 0 V. For bi-directional models, 12 mA for current outputs, 2.5
V for 5 V models and 5 volts for 0 to 10 V models.
Span – PJ3 jumper must be in “H” position to calibrate the span and PJ7
jumper must be in the “H2O” position.
Note: If you must calibrate in Pa mode with the PJ7 jumper in the Pa
position, you must calibrate the unit to the full scale inches of water
column equivalent for proper calibration. For example: 5 in w.c. full scale
models the equivalent required is 1250 Pa.
Also, the PJ5 jumper should be set to “ZC” on a bidirectional unit and “N”
on a unidirectional unit. Connect the pressure source and apply the high
range rated pressure. When the pressure has stabilized, press and hold
the “Span” switch for about 4 to 5 seconds. The display, if present, will
now read the calibration pressure. Span may only be calibrated on the
highest range for the unit.
Restoring Factory Calibration Coefficients:
The user calibration does not affect the factory calibration coefficients.
The factory defaults are easily restored if the user calibration must be
“erased”. Simultaneously press both the “Zero” and “Span” buttons and
hold them for approximately 4 to 5 seconds. The factory calibration
should now be restored.
MAINTENANCE
Annual recalibration is suggested. No lubrication or other periodic
servicing is required. Keep exterior and cover clean. Occasionally
disconnect pressure lines to vent both sides of gauge to atmosphere and
re-zero. Do not use solvent to clean transmitter. Use only plastic
compatible cleaners or water. The Series MS is not field serviceable and
should be returned if repair is needed (field repair should not be attempted
and may void warranty). Be sure to include a brief description of the
problem plus any relevant application notes. Contact customer service to
receive a return goods authorization number before shipping.
©Copyright 2013 Dwyer Instruments, Inc. Printed in U.S.A. 10/13 FR# 01-443337-00 Rev. 8
DWYER INSTRUMENTS, INC.
Phone: 219/879-8000 www.dwyer-inst.com
P.O. BOX 373 • MICHIGAN CITY, INDIANA 46360, U.S.A. Fax: 219/872-9057 e-mail: info@dwyer-inst.com
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