Tektronix MAO-12 Addenda to the MetraBus User's Manual 24816A User manual
MAO-12 MAO-12
Addenda to the MetraBus User’s Manual Addenda to the MetraBus User’s Manual
Keithley MetraByte Corporation Keithley MetraByte Corporation
440 Myles Standish Blvd 440 Myles Standish Blvd
Taunton, MA 02780 Taunton, MA 02780
Part Number: 24816
First Printing: June 1988
Copyright 0 i
MetraB e Corporation
440 Myles
Taunton. Massachusetts 02780
MetroByte Corporation assumes
product. This product is not desi
use in life support or critical app Ications.
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Information furnished b
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MetraByte Corporation is believed to be accurate and reliable.
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no liability for damages consequent to the
ned with components of a level of reliability suitable for
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andish Boulevard
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MetraByte” is a trademark of MetroByte Corporation.
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MAO-12 ANALOG OUTPUT BOARD
Features of the MAO-12
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MetraByte’a
Industrial Data Acquisition and Control System. It has 8 independent output channels,
each with 12-bit (1 part in 4095) resolution. The MAO-12 has five standard switch
selectable voltage output ranges as well as 4-20 mA output capability. Provisions have
been made for the installation of additional resistors allowing a wider range of output
gains to be selected. Screw terminals on the board will accept 12 to 22
The MAO-12 connects directly to one of three MetraBus driver cards (MDB-64, MID-64,
or REM-64) and computer via a 50 conductor ribbon cable. The MetraBus cable
connects the MAO-12 to one of the driver cards and carries all data, address, and
status information as well as distributing power on the MetraBus. A total of 20 ground
lines are interleaved among the data and address lines to ensure noise immunity. The
MetraBus system was desi ned to allow MetraBus cable lengths of up to 100 feet.
Remote control of the !i Metra us system is possible via the REM-64 serial driver card at
distances of up to 1.2 Kilometers. The MAO-12 is 19” rack mountable in either a
standard NEMA type enclosure or the MetraByte RMT-02. The MAO-12 may also be
mounted on any flat panel or other flat surface.
Interlaces
Unipolar, Bipolar, and 4-20 mA outputs
12-bil Resolution (1 part in 4095)
Remote signal coimktions
UD 10 64 analog outputs per
Ekremely cost-effetiive
Compatible with most computer languages
directly with IBM PC/XT/AT and compatibles
computer expansion slot
MAO-l 2 is an 8 channel analog output board for use with the MetraBus
AWG wire.
Because of its design, the MetraBus system allows for control of up to 64 analog output
channels (6 MAO-12s) from a single computer expansion slot making it the most cost
effective Industrial Data Acquisition and Control System available.
Some of the more common uses of the MAO-12 include computer control of 4-20 mA
Process Control Equipment, single board Function Generator, ON/OFF Servo Motor
Controller, Digital Attenuator, Vanable voltage source, and much more.
MAO-l 2 Functional Block Diagram
The MAO-12 acts as the interface between your application signals and the MetraBus
driver card and computer. The block diagram below will aid in visualizing control signal
flow from the driver card through the MetraBus cable and out to the MAO-12 and your
application signals.
Auxiliary Power Supply
The MAO-12 requires f15 V in addition to the standard t5 V required by all MetraBus
l/O boards. Therefore a high quality external power supply such as the PWR-55 or
PWR-100 is needed (see current MetraByte Catalog for details of the PWR-55 or
PWR-100). The use of an auxiliary supply in conjunction with the MDB-64 driver card,
requires that fuse Fl be removed from the driver card.
!nstalllng the MetraBus Controller/Driver Card
In order to use your MAO-12 or any other MetraBus I10 board, you must configure and
install one of three interface/driver cards (MDB-64, MID-64. or REM-64). See the
relevant sections of this manual for the installation procedure.
Setting the MAO-12 Board Address
Each MAO-12 connected to a single MetraBus cable must be set to a unique,
non-overlapping MetraBus I/O address. Each of the eight channels on the MAO-12
uses one of the available 64 .MetraBus I/O addresses. The eight channel addresses run
consecutively starting from the MAO-12 Board Address. Setting the Board Address is
outlined below. (The diagram shows a typical BOARD ADDRESS switch setting):
1)
2)
3)
t
2 3
The address DIP switch on the MAO-12 is located above and to the left of the
MetraBus interface connector. The numbers silk-screened above each switch
indicates its value when enabled.
To set the Board Address, simply turn ON those switches corresponding to the
address you have chosen. For example, in order to set a Board Address of 16,
the switch with a value of 16 immediately above it should be turned ON while the
others would remain OFF. The MAO-12 uses 8 of the available 64 MetraBus I/O
addresses. The MAO-12, like all MetraBus I/O boards, requires a non-overlap
ping address in order to avoid address conflicts when being accessed by the
driver card. Since any MetraBus I/O board may be connected to a single
MetraBus cable address overlap is possible. Use caution to avoid this.
After setting the MAO-12 Board Address, you may connect it to the MetraBus
cab\&. It is good practice to remove power from the MetraBus cable prior to
connecting I/O boards. The connectors are keyed for your protection. Check the
keyways for correct alignment prior to plugging in the MetraBus cable. Do not
force the connectors!
2
4)
Reset Respond Jumper
The MAO-12 may be configured to RESET all DAC outputs to 0 volts, CLEAR the
simultaneous update register, and RESET the channel selection to CHO. Placing
jumper J2 over the rightmost two pins will cause the MAO-12 to CLEAR and RESET the
board as defined above, whereas jumper placement over the leftmost two pins will
cause the MAO-1 2 to maintain status quo at power-up or software clear.
MAO-12 Output Range, Polarity, and Reference Selection
Each channel on the MAO-12 can be set at any of 5 standard output ranges (ti.5V,
+5V, f5V, +l OV, fl OV). Range selection is accomplished via a 3 station slide actuated
switch assigned to each channel. The channel/switch assignments are marked an the
MAO-12 and are shown below. The position of each switch with respect to Full Scale
Output Range is also shown below.
If you have only one MAO-12 or if your MAO-12 is last board in your system, you
should install the resistor terminatin networks that were provided with your
MetraBus driver card. The sockets 8 Nl and RN2 on the MAO-12 are for this
urpose. These resistor networks are used to minimize signal reflections due to
P
ong cable lengths. They are optional, however, and have little effect for
MetraBus cables of 50 feet or less.
CH #O-Q SW6
CH #l--z. SW7
CH#2-’ ET!
EL! ii -c
CH #5 1, :bY:
CHiY6 --> ZE CH #7 ->
MAO-12 OUTPUT SIGNAL CONNECTIONS
Output signals from the MAO-12 may be wired directly to the output connector. The
connector has output assignments silk-screened adjacent to their assigned terminals on
the board.
WE
O-1 OVdc
&5Vdc
&2.5Vdc
510 Vdc
3
4-20 mA Output
The MAO-12 has provisions for 4-20 mA current output. This is often useful when
connecting the MAO-12 to certain types of industrial instrumentation. The 4-20 mA
current output consists of a precision current sink formed by a VMOS power FET and
reverse protection diode. The drawing below illustrates such a circuit.
A minimum of 6 volts must be maintained across the output circuit for proper operation.
The maximum voltage across this circuit should not exceed 36 volts for power
dissipation reasons. Therefore, a 36 V or 24 V loop supply such as the ACCULEX
model PSLOOP-175 (24 Vdc @ 175 mA) is ideal.
The 4-20 mA output from the MAO-12 requires that several decisions be made prior to
use. They concern the
or 36V supply is
neede
wa 4 s to configure the process loopwit grounded supply. The ground 3
pe of power supply and its rating. As mentioned above, a 24V
to supply adequate power to the output circuit. There are two
2
rounded
load with floating supply or floating load
supply-floating load configuration allows several
loops to be powered from the same supply but dictates that the load be 2 wire floating.
The wirfng scheme for both of these configurations is illustrated below. Choose the
one which best suits your needs then wire your output accordingly.
1)
Set the channel output range to 5 VFS Unipolar as instructed in the “Output
Range, Polarity, and Reference Selection” section above.
2)
Wire either the (+) side of the Floating supply or one side of the Floating load
(depending upon the configuration chosen) to the I OUT terminal’ of the MAO-12
as illustrated above.
3)
Wire the (-) side of the supply or the other side of the Toad to the Analog RTN
terminal of the MAO-12.
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