DS Europe 500QD Series, Инструкция по эксплуатации

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8.6 WORKING AREA OF THE CURRENT AMPLIFIER -A4: (2 -wires):
NOTE: see the diagram of the "Pressure transducer" valid also for the current amplifier
-A4 of the load cells.
8.6.1 The diagram states the relation between the Power supply voltage: Vps of the cell
(=abscissa) and the load resistor value: RL (= ordinate).
The amplifier -A4 rightly works within all the points of the "Area of Vps "defined by
the line (on the left) of "minimum Vps allowed" and by the line (on the right) of
"maximum Vps allowed".
Great attention has to be put on the choice of the electronics to be connected to the
self-amplified cell (-A4) regarding the supply voltage (= Vps ) and the load resistor
(=RL).
The best acceptable points of the working area (= "area of Vps ) have to be 15÷30%
far from the left line (= minimum Vps allowed) within the "Area of Vps ".
It is not convenient to exaggerate on the supply voltage (= Vps ) to avoid useless
thermal dissipation inside the transducer.
Two explanatory examples:
1) RL = 250 ohms = external load resistor.
Supply voltage = Vps = 15 V:
not sufficient.
" " " = 17 V: just at the limit; not advisable.
" " " = 20÷24 V: advisable.
" " " = 28 up to 41 V: not advisable; useless thermal
dissipation.
2) RL = 750 ohms = external load resistor.
Supply voltage = Vps = 24 V: not sufficient.
" " " = 27 V: just at the limit; not advisable.
" " " = 30 V: advisable.
" " " = 35 up to 43 V: not advisable; useless thermal
dissipation.
Low values of RL and of Vps are always preferable (the example 1 is preferable to
the example 2).
Due to the limitations and to the disadvantages of the current amplifiers -A4 are
always advisable the voltage amplifiers; particularly the version -A5 (= output ±5 V).