Interface Specifications; Analog Level Input; Level Arbitration; Analog Outputs - Accusonic 8510+ series Reference Manual

Interface Specifications

Analog Level Input

Level is input in 4-20 mA analog form, from an external current loop source. Both terminals at the
flowmeter must be within 20 volts of ground for operation. The external device should be configured to
give increasing current for increasing water depth. If it is configured to give increasing current for
decreasing water depth, the Level Arbitration will not operate correctly. For Level sensors requiring d.c.
power, 24 Volts dc (at a total maximum current of 0.5 A) is available from the Level input terminal block.
Configuration of the Level input is defined by user-defined parameters. A parameter makes allowance for
alternative load resistances to be placed across the input terminals. Normally the input resistance is 100.
For electrical characteristics see "Electronic Unit" Specifications, page Electronic Unit2-1.
A Level input having an electric current (in mA) less than the value set by the parameter Min mA

Input, or more than 21.0 mA is treated as being in a "fault" state.
Level inputs between the value set by the parameter Min mA Input and 20.00 mA are interpreted as

elevations in feet or meters, linearly interpolated in the range from 4.00 to 20.00 mA, between the
values stored under the parameters 4mA Level Input & 20mA Level Input.

Level Arbitration

Applies when two Level inputs are allocated to a Section. Both inputs must be configured to give

increasing current for increasing water depth. Input #1 is the lower numbered input allocated to the
section.
If input #1 is between the value set by the parameter Min mA Input and 19.8 mA, the value scaled by

the parameters 4mA Level and 20mA Level is used as the arbitrated value for Level. Input #2 is
ignored.
If input #1 is below the value set by the parameter Min mA Input, it is rejected. If at the same time,

input #2 is between the value set by the parameter Min mA Input and 20.0 mA, the scaled value from
input #2 is used as the arbitrated value for Level.
If inputs #1 and #2 are both below their values set by the parameters Min mA Input, both are rejected,

and no Level value is available. The flowmeter is declared failed.
If input #1 is above 19.8 mA, and input #2 is not rejected, then the arbitrated level is the greater of that

indicated by input #1 or input #2.
If input #1 is above 19.8 mA, and input #2 is rejected, then Level is that indicated by input #1.

Usually input #1 reading 20mA indicates pipe full. Input #2 is usually scaled for a larger range than

#1.

Analog Outputs

These are configured for 4-20mA, and may be separately allocated to give a linear representation of the
flow, level, average water velocity, water temperature or sum of section flows. If desired, the outputs may
be scaled to cover any range of the variable from reverse, through zero, to forward: it is necessary only to
define the output by the extremes of the range (i.e., at 4mA and 20mA). Output allocation to flowmeter
General Specifications 2-5