Datasheet

2 Fluke Corporation Fluke 750P Series Pressure Modules
Quick and easy measurements
Fluke 750P Series Pressure Modules are easy
to use. To measure pressure, connect the pres-
sure module to a pressure source or hand pump
and then connect the pressure module cable to
the calibrator. Apply pressure from the pressure
source and it is displayed digitally on the calibra-
tor. At the touch of a button, the pressure may
be displayed in up to 11 different engineering
units. When used with the 750 Series Document-
ing Process Calibrators, pressure readings can be
date/time stamped and stored electronically for
later retrieval. This saves time, eliminates errors,
and supports compliance with quality standards
and regulations.
Pressure module performance
and technology
Fluke 750P Series pressure modules are highly
accurate, with specifications that apply from
0°C to 50 °C (32 °F to 122 °F), a feature that sets
them apart from other pressure calibrators. Many
ranges have total uncertainties of 0.04 % of full
scale and reference uncertainties of 0.01 % of full
scale (see specification table).
This performance is possible through the
innovative application of mathematics and micro-
processor power. Fluke pressure modules have
silicon piezo-resistor sensors which consist of a
resistive bridge fabricated in a silicon diaphragm.
Pressure applied to the diaphragm causes a
change in the balance of the bridge which is
proportional to the applied pressure. The bridge
balance change is not linear and is very sensi-
tive to temperature. However, since these effects
are quite stable with time and with repetitive
changes of condition, the sensors are carefully
characterized.
During manufacture, Fluke pressure module sen-
sors are characterized by reading temperature
and pressure at multiple points. A least-squares
regression is used to calculate the coefficients of
a polynomial expression for pressure. The coeffi-
cients, unique to that pressure module, are stored
in the module’s memory.
Each module has its own microprocessor, allowing
it to run the measurement circuitry and to commu-
nicate digitally with a calibrator. When connected
to the calibrator, the modules coefficients are
uploaded from the pressure module to the calibra-
tor. Then, as pressure measurements are made,
raw sensor values for pressure and temperature are
digitally loaded to the calibrator, where the raw
sensor values and coefficients are manipulated to
derive and display the pressure reading.
This innovative technique provides several
benefits:
1. Digital communication eliminates errors due to
poor connections and electrical interference.
2. The modules are inherently temperature-
compensated from 0 °C to 50 °C (32 °F to 122 °F).
3. The modules are fully interchangeable because
all measurements are completed in the pres-
sure module itself and then communicated to the
calibrator in digitized form. Modules are cali-
brated independently of the calibrator, and can be
used with any 740, 750 or compatible 720 or 710
series calibrator. Each module has its own serial
number to maintain independent traceability.
Sensor protection in isolated modules
Many of these modules (see table) incorporate a
stainless steel diaphragm to isolate the sensor. With
these modules, any medium that is compatible with
stainless steel can be used on the high side of the
module.
Rugged construction
A urethane overmolding protects against shock if
a module is accidentally dropped and also seals
against dirt, dust, and moisture. Pressure connec-
tions are ⅛” NPT female connection. A ¼” NPT
Male, ¼” BSP/ISO and M20 male adapter are also
provided with each pressure module.
Convenient setup
A one-meter cable between the pressure module
and calibrator reduces the length of connecting
tubing to the pressure source. The remote pressure
head also provides an extra margin of safety and
convenience by removing the calibrator and
operator from the pressure source in the event or
need for semi-remote measurements.