Crystal MultiCal KPA-PSI User Manual

MultiCal Instruction Sheet

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kPa/PSI Pressure Module

Introduction

MultiCal pressure modules are used to measure pneumatic or hydraulic pressures. They can
also be used to measure vacuum.

MultiCal modules don’t display
pressure, since they only have
an electrical output. Instead, the
modules convert pressure to
millivolts. Modules are used with
devices capable of measuring
DC millivolts, such as a digital
multimeters or oscilloscopes.

MultiCals are calibrated to convert
pressure units (for this model, inches kPa
or PSI) to 1 millivolt per pressure unit. Vacuum
readings will of course be negative.

Pressure is measured by connecting an appropriate fitting to one of the two 1/8″ female NPT
ports (plug any unused port). Any gas or liquid compatible with 316 stainless steel, PTFE
(polytetrafluoroethylene) impregnated hard anodized aluminum, and buna-n rubber, can be
applied to the module as the pressure source.

The three-position switch acts as a power switch as well as selecting kPa or PSI scaling
for the output. The OFF position is used to measure the internal battery condition via an
external multimeter.

MultiCal modules perform best when used with high accuracy multimeters. We recommend
meters manufactured by the Fluke Corporation, but MultiCals can be used with any meter
that has 10MΩ or greater input impedance, and (preferably) 4mm banana jacks on 19mm
(3/4″) centers.

When used with a high performance multimeter, the pressure adapter becomes more
than just a “digital pressure gauge”. By using the features built-in to the Fluke 87 for

example, the system becomes a datalogger capable of measuring and recording peak high,
peak low and average pressures.

This manual includes instructions for calibrating the module itself, but we also offer repair,
calibration/certification services. MultiCals are manufactured (and serviced) by a company
that only makes pressure measuring instruments. It’s the only thing we do and that’s why we
say: Pressure is Our Business!

C R Y S T A L

engineering corporation

PN: 1763 Rev C, 4/2004

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PN: 1763 Rev C, 4/2004
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PRESSURE is Our BUSINESS

™

Operating Instructions

To ensure safe and accurate operation, please be familiar with the following operations and
functions.

WARNING:

Severe injury or damage can occur through improper use of pressure instruments!

Do not exceed recommended pressure limits of tubing and fittings. Be certain all pressure
connections are secured. Never disconnect pressure instrumentation without first relieving
system pressure.

CAUTION:

Never insert any object (other than a 1⁄8″ NPT fitting) into the inlet ports. The sensor
diaphragm is very thin and can be damaged or destroyed by solid or sharp objects. Clean
the sensor with appropriate solvents, only.

The internal pressure sensor measures the difference between atmospheric (barometric)
pressure, and the pressure (or vacuum) applied to the pressure port. The pressure being
measured can be either liquid or gaseous, providing it is compatible with the materials listed
in the specification section.

PTFE tape should be used with any fittings installed into either of the 1⁄8″ female NPT ports.
Two ports are provided so that additional tees should not be required. Plug any unused
ports.

MultiCals have been calibrated for use with meters that have 10MΩ input impedance, as do
most handheld meters, and some benchtop multimeters. If your meter has higher or lower
input impedance, add 0.1% to the specification of the MultiCal, or refer to the Calibration
section of this manual for other methods of eliminating the error introduced by an impedance
mismatch.

Pressure Measurement

Follow this procedure to correctly use the MultiCal pressure module.

1. Plug the MultiCal directly into the voltage input terminals of the multimeter or with the
patch cord set. The patch cord set consists of a 48″ cord with double banana plugs
on each end and a double banana jack splice. Plug the splice into the MultiCal and
the patch cord into the splice. Plug the other end of the patch cord into the multimeter.
Polarity is marked on the MultiCal and on the patch cord and splice.

2. Set the multimeter to the millivolt (DC) range.

3. Check the battery condition: With the MultiCal still in the OFF position, the
multimeter must indicate a minimum reading of 100 mV. Readings less than 100 mV
indicate the battery must be replaced. To be sure that your pressure measurements are
accurate, always check the battery condition first, and replace the battery if necessary.

4. Turn on the MultiCal by sliding the switch to the range you intend to use.

PN: 1763 Rev C, 4/2004

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C R Y S T A L

engineering corporation

5. “Zero” the MultiCal. Without any pressure or vacuum applied to the module turn the
knob opposite the banana plugs until your meter reads precisely zero. Prior to taking

measurements, and recommended when changing scales, the module should be
“zeroed” at barometric pressure.

Most multimeters “forget” the “relative” setting when changing from mV to any other

scale, even just to Volts. Some meters autorange from mV to Volts and then lose the
“relative” value. In these cases the zero knob may be more convenient than the “relative”
button on the multi-meter.

The zero reading may also shift when the MultiCal is shifted from a vertical to a

horizontal orientation. This is due to the oil filling that transmits the pressure signal
from the stainless steel diaphragm to the silicon pressure sensor. The magnitude of the
shift is typically 0.07 kPa or less.

6. Apply pressure to the MultiCal. If the meter reads overrange, change the multimeter
range to DC volts (instead of mV). Note: The decimal place will be for volts. Multiply the
reading by 1000. For example, 0.200 V would be 200 kPa.

Battery Replacement

1. Set the power switch to the OFF position.

2. Disconnect the MultiCal from the multimeter and any pressure connections.

3. Turn the MultiCal so the power switch is facing down. Remove the single screw located
between the banana plugs.

4. Grasp the one case half in each hand. Pull the two halves apart, beginning at the end
with the banana plugs.

5. Remove and replace the battery.

6. Reassemble the MultiCal. To reassemble, mate the two case halves at the end opposite
the banana plugs, then “snap” the two halves together.