AccuLoad IV Installation & Maintenance Manual
Installation 38
• Dual Channel with Integrity—Four pulse inputs receive two pulses streams and two inverted pulse
streams from the meter. This enables the AccuLoad to detect the direction of flow and meter connection
problems, including when both pulse streams are inactive.
For each of the above meter pulse modes, the signal on the input to the AccuLoad must be less than 1 volt
for a minimum of 80 microseconds and then transition to greater than 5 volts and remain above 5 volts for
a minimum of 80 microseconds to qualify as a valid pulse (as shown in the following graph).
3.6.6 Analog I/O Modules
The A4M board has six slots into which modules can be inserted to interface to analog sensors or actuators
(such as a pressure sensor or valve). Typically, these modules are installed at the factory, but changes and
replacements of these modules may be done in the field. The analog I/O points are fully configurable and can
be inputs (such as temperature or pressure) or outputs (such as analog valve control). Five types of analog
interface modules are available, which are inserted into a socket on the A4M board as described in the
following table.
Table 19: Types of Analog I/O Modules
Analog Module Type Electrical Connection Functions
Resistive temperature
device (RTD)
Four-wire, 100-ohm RTD Temperature input
CRI 4-20 mA input Temperature, pressure, and density
General purpose input
CRO 4 to 20 mA output Analog valve control
Flow rate output
General purpose output
VTI 1 to 5 VDC input Temperature, pressure, and density
General purpose input
VTO 1 to 5 VDC output Analog valve control
Flow rate output
General purpose output
Figure 24: Meter Pulse Requirements
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