Compaq MTEK6000 - Manual (Page 39)

MTEK6000 SERIES USER'S MANUAL
January 2002 4 - 1
CHAPTER 4: OPTIONAL EQUIPMENT
ANALOG OUTPUT (AO) OPTION
The Analog Output Module (part # 1021-
0001B-001) and connecting cable (part #
1002-0245B-001) provides a two-wire,
loop-powered, optically isolated, precision
4-20mA output. This module interfaces
with the MTEK6000 series product line to
provide a 4-20mA output for flow rate,
pressure, or numerous other control and
monitoring applications. Up to two modules
can be installed in the MTEK6000 in place
of the batteries by using the AO module
adapter plate, (Metretek stk #1008-0011B-
001).
Power for the digital interface section of the
AO is selectable by using the DIPswitches,
and can be supplied by Vcc of the
MTEK6000 or from the main supply
voltage. The AO module interfaces to an
MTEK6000 series product via the standard
I
2 C serial interface bus. The MTEK6000
unit requests the desired mA output from the
AO module using this bus. An I
2 C digital
I/O chip is used to send the information to
the analog output section of the AO board.
The analog output section of the board
derives its power from the current loop, and
is optically isolated from the digital control
interface section. The analog output section
receives commands from the digital I/O chip
through opto-isolators. Commands are in
the form of a serial data stream. The AO
module provides 4-20mA output signals
with a resolution of 1 part in 65536 (16 bit).
The D/A also allows for over-ranging of the
output to a minimum of 3.5mA and a
maximum of 24mA. The field interface to
the D/A is a simple two-wire connection.
Reverse polarity protection is provided.