Corel Ventura
TI 097P/00/en
Pressure Measurement
commutec PMX 67…
Evaluation unit for Cerabar pressure transmitters
with PFM transmission
Commutec PMX
7 HP (35mm) wide
Racksyst plug-in board
as a single-channel or
two-channel instrument,
with or without LCD display and operating keys.
Pressure Evaluating Instrument
The microprocessor-controlled
Commutec PMX instruments create the
intelligent connection between the
measuring sensor and the signal output
in the production process.
Two main features of this pressure
evaluator are
• The accurate digital selection of the
measuring range without the need for
calibration equipment.
• Simple setting up for process control
and two-point regulation by software
based matrix programming.
Self-monitoring indicates continuously
the correct operation of the measuring
The software used is specifically for
supporting the operation of Cerabar
pressure transmitters with PFM signals
for process pressure measurement or
electrical measurement of differential
Using a PC for parameterising and
visualising systems and for the
integration of data streams in a
production plant, the intelligent
Commutec PMX pressure evaluating
instrument is a significant step towards
“plant-wide control”.
Instrument Versions
Commutec PMX 671 Z
Single-channel pressure instrument
with LCD display and operating
Commutec PMX 672 Z
As the Commutec PMX 671 Z but
with two channels and ideal for the
electrical measurement of differential
Commutec PMX 676 Z
The cost-effective single channel
instrument for external display and
remote operation, with the
Commulog VU 260 Z or with a PC
using a ZA 672 computer interface.
Commutec PMX 677 Z
As the Commutec PMX 676 Z but
with two channels and ideal for the
electrical measurement of differential
• Process pressure measurement
• Electrical differential pressure
measurement e.g. filter monitoring or
pump control
• Direct control or two-point regulation
of pressure using integrated limit
contacts e.g. in compressed air lines
• Pressure compensation for flow
measurements of gases and steam to
determine consumption.
Endress + Hauser
Nothing beats know-how
The Complete
Measuring System
The Commutec PMX supplies the power
to the Cerabar pressure transmitter by
unscreened two-core cable.
The Commutec receives a
pressure-dependent pulse frequency
modulated (PFM) signal from the
pressure transmitter to ensure high
quality signal transmission.
p1- p2
Limit value
Limit value
Input 2
Input 1
(p1 > p2)
Operating Ranges
Intelligent Calibration
The measuring range required is
adjusted directly without the need for
any external electrical or mechanical
calibration aid. Only the nominal values
for zero point and sensitivity, as stated
on the name plate of the Cerabar, need
to be entered into the Commutec. This
simple calibration step is all that is
required to give an immediate and
accurate pressure reading which is
shown on the digital display.
Function Monitoring
The pressure evaluating instrument, with
a built-in microprocessor, is
self-monitoring from the Cerabar
pressure transmitter right up to the
All Commutec instruments can be
accessed on-site with the hand-held
commulog VU 260 Z, so that measured
values and stored parameters can be
called up and interrogated during
measurement without affecting the
current output. This feature can be used
for on-line access or altering the units of
pressure, limit values or switching
This information can be shown in the
display of the Commutec PMX 671 Z
and 672 Z measuring instruments which
also have operating elements.
Commutec application
for pump control. The
two-channel PMX 672 Z
instrument ensures
monitoring of the entire
Signal evaluation
The analogue output signals are
standard 0...20 mA or 4...20 mA
currents and 0...10 V or 2...10 V
voltages, depending on calibration.
They are proportional either to the
system pressure or to the differential
• Any initial or end value can be
accurately set digitally for the 0/4 to 20
mA output.
• The measuring span can be adjusted
within 10 to 100% of the maximum
measuring span of the Cerabar.
• Two limit relays, each with one
potential-free change-over contact,
are built into the Commutec. These
can be operated independently of
each other in minimum or maximum
fail-safe mode and with any hysteresis
spread, for two independent two-point
Minimum (Maximum) fail-safe mode:
The relay de-energises when the level
falls below (rises above) the switching
point or if an error occurs.
• The error indication has a
potential-free change-over contact
with the relay de-energising when an
error occurs. The instrument can be
easily programmed to drive the
analogue signal to -10 % or +110 %
level or to retain the last measured
value should a fault occur.
• Connecting a single Cerabar to a
two-channel instrument allows both
current outputs to be programmed
separately so that a magnification
mode can be assigned to one of the
Connection to
Automation Systems
The bus signals from the Commutec
PMX are converted by the ZA 672
computer interface into standardised
RS 232 C interface signals. This allows
dialogue with larger automation systems
for greater flexibility.
Up to 64 measuring points installed with
this configuration can be controlled and
operated on-line from the control room.
Every Commutec PMX also has
conventional outputs (0/4...20 mA,
0/2...10 V) for independent operation.
0/4...20 mA
RS 232 C
Every Commutec PMX
is equipped with a
two-core Rackbus. The
common ZA 672
interface board
connects the transmitter
to larger automation
Racksyst plug-in boards must be
installed outside explosion hazardous
areas in a rack or in a protective
The following are available from E+H:
• The 19" wide rack for mounting in the
control room with slots for 12
Commutec PMX instruments side by
side installation
• The half 19" wide field housing with
Protection IP 65
• Monorack housing (7 HP) for single or
row mounting in the control panel.
instrumentation with the
Monorack housing. Four
extra instruments can
be connected side by
side on the right or to
the left.
Construction, Materials,
Racksyst plug-in board:
conforming to DIN 41494
(Eurocard format)
Technical Data
Front panel: black synthetic with blue
field inlay, grip and markings
Protection: Front panel IP 20,
board IP 00 (DIN 40050)
Weight: approx. 0.3 kg
Dimensions of the
Commutec PMX
Operating temperature:
Storage temperature:
Electrical Connection
Connection positions
for the connecting strip.
Grey coloured
connections are
available for
Plug connection
Multipoint plug:
conforming to DIN 41612, Part 3,
Type F (28-pole)
Coding pins in the multipoint strip:
PMX 671 Z/672 Z in Position 1 and 26
PMX 672 Z/677 Z in Position 1 and 27
Power Supply
DC voltage: 24V (20V...30V)
Permissible residual ripple: 2V
(Vpp within tolerance)
Power current:
approx. 90 mA, max. 125 mA,
integrated fine-wire fuses
Signal Inputs
All Cerabar PMC pressure transmitters
with a PFM signal are sensors which
can be connected to the galvanically
isolated input.
• 2-core connecting cable max. 25 Ω
per core, unshielded, shielded or
multicore for signal circuits.
Signal outputs
• Current output: 0...20 mA, selectable
to 4...20 mA, RL max. 500 Ω
• Voltage output: 0...10 V, switchable to
2...10 V, RL min. 10 kΩ
• Limit values
Two independent relays each with an
adjustable change-over contact,
switching point and switching
hysteresis set as required
Quiescent current in fail-safe mode:
Minimum or maximum, selectable
• Fault / Warning Indication:
one relay with potential-free
change-over contact
• Switching consumption: max. 2.5 A
max. 250 V alternating current
max. 300 VA at cos ϕ = 0.7
max. 100 V direct current max. 90 W
• Rackbus: Data rate 19 200 bit/s
2-core, bidirectional cable
Type of protection Commutec PMX:
[EEx ia] IIC
PTB Nr. Ex-88.B.2048 X
for the PMX 671 Z and PMX 676 Z and
PTB Nr. Ex-88.B.2050 X
for the PMX 672 Z and PMX 677 Z.
Direct Calibration of the
PMX 671 Z and PMX 672 Z
The Commutec PMX 671 Z and 672 Z
can be directly calibrated and
interrogated using the front panel keys.
Only six keys and a table (matrix) are
required. The matrix field to be selected
is called up with the V and H keys and
the data entered using the other keys
(the operating matrix card is clipped
onto the side of the instrument). The
matrix field selected is indicated
preventing errors when reading off
measured values or when entering data.
During operation, the LCD display
shows pressure or differential pressure
in the units selected or as a percentage.
Interactive Facility
Front view of the
The grey operating
elements underneath
are only available with
the PMX 671 Z and the
PMX 672 Z.
The display shows
• 4-digit field floating
decimal point for
system pressure or
differential pressure
• Bar diagram for end
value (10-step bar
• Selected matrix field
V, H selecting matrix
E confirming data entry
→ Selecting the
decimal point position,
+/– increase/decrease
External Operation
Only with the Commutec
PMX 676 Z and PMX 677 Z
The Commutec PMX 676 Z and 677 Z
are calibrated and interrogated for
operation status using the Commulog
VU 260 Z.
External and Remote Operation for
all PMX Instruments Using the Commulog VU 260 Z
Operating the Commutec can be simply
carried out using the Commulog
handheld terminal. In dialogue with the
PMX, data is exchanged which is shown
with supplementary information in plain
language on the large display of the
VU 260 Z.
Commulog VU 260 Z
Commutec PMX
instruments can be
interrogated and
parameterised in plain
language using the
handheld terminal.
• The green and red LEDs in the central
field can be seen from a distance and
show if the limit signal relays are
de-energised or energised and so
clearly indicate if a critical condition
has occurred.
• The green LED below indicates
whether the Commutec is in dialogue
with the ZA 672 or the Commulog
VU 260 Z.
• An error or warning is indicated by the
red LED at the bottom which remains
lit to indicate an error or flashes to
indicate a warning.
For example, a warning can be due to
faulty operation while an error occurs
when no signal is received due to, for
example, cable breakage,
short-circuiting or a function error of the
Status Display
green LED (left)=
relay energized
red LED (right)=
relay de-energized
green LED=
remote dialogue
red LED=
Commutec PMX 671 Z
Order No.: PMX 671 Z-A 0E 1A1
Single channel pressure measuring instrument with LCD display and operating
Commutec PMX 672 Z
Order No.: PMX 672 Z-A 0E 1A1
Two-channel pressure measuring instrument with LCD display and operating
Commutec PMX 676 Z
Order No.: PMX 676 Z-A 0E 1A1
Single-channel pressure measuring instrument for external operation
Commutec PMX 677 Z
Order No.: PMX 677 Z-A 0E 1A1
Two-channel pressure measuring instrument for external operation
Further Specifications for a
Complete Measuring System
• Cerabar PMC with PFM signal
(state version)
• Accessories (rack or
housing, multipoint strip)
Project Planning for Racksyst
racks or Racksyst field housing
with self-adhesive labels for
wiring (state instrument version)
Technical Information TI 047F/00/e
System Information SI 004P/00/e
Cerabar PMC 133
Technical Information TI 105P/00/e
Cerabar PMC 531…536 Z
With diaphragm seal.
For food and process industries
also for EEx applications
Technical Information TI 095P/00/e
Other applications for the Commutec
system are found in the
measurement of level, flow, bulk flow,
moisture, and analysis technology.
The Technical Information required
will be sent on request.
Cerabar PMC 430 Z
Precision Pressure Transmitter
also for Ex applications
Technical Information TI 091P/00/e
Instruments International
P.O. Box 22 22
D-79574 Weil am Rhein
Tel. (0 76 21) 9 75-02
Tx 7 73 926
Fax (0 76 21) 9 753 45
Endress + Hauser
Nothing beats know-how
TI 097P/00/en/11.92
Printed in Germany/UE
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