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2.3.4 Display Backlight
The display backlight will be automatically enabled upon connection of an external DC
voltage supply in the range of 12-30V; the backlight is not available when operating on battery
or loop power. If it is required to reduce power consumption while operating on external DC
power the backlight can be overridden in the Advanced Menu (see section 5.10).
2.3.5 Analogue Output
The loop powered 4-20mA Analogue Output is a passive non-isolated output capable of
retransmitting the flowrate to remote instrumentation or control systems such as a PLC or
DCS. The Analogue Output can be spanned anywhere within the operating range of the
associated flowmeter; both the 4mA and 20mA points are software programmable in the units
selected for the Rate display. The instrument will over-range to 22mA which allows the user to
identify when the system is exceeding its maximum normal flowrate (i.e. identifying a fault
condition).
The Analogue Output accuracy is ±0.05% of Full Scale (0.01mA) at a regular ambient
temperature of 25
o
C. Due to the effects of temperature changes on the internal components,
the accuracy will become progressively worse as the ambient temperature moves further
away from 25
o
C; up to a worst case of ±0.25% of Full Scale (0.05mA) at the extremes of the
instrument’s operating range (-30
o
C or +80
o
C)
If required, the Analogue Output can be software adjusted to achieve the best accuracy
under the specific operating temperature of your installation. The 4mA and 20mA points are
both adjustable in 0.001mA increments by accessing the Analogue Output Adjustment section
of the Advanced Menu (see section 5.10 of this manual).
2.3.6 Unscaled Pulse Output
The Unscaled Pulse Output function is used to retransmit the input signal from the
associated flowmeter; it will maintain the same frequency and duty cycle as the input signal.
When setting up a system with two separate Total displays on two separate instruments the
Unscaled Pulse Output is the best method of transmitting the Total value to the secondary
totalising instrument.
The Unscaled Pulse signal can be transmitted as an NPN signal from the passive digital
output, or as an NPN or PNP signal from the isolated digital output. The passive digital output
can be used on battery power, however transmitting the signal via the isolated output will
require an external DC power supply.
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General