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Instruction Manual MM850099 ed.02a
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4
FUNCTIONAL DESCRIPTION
The block diagram of the
UniCal mA
portable calibrator is shown in the figure below:
D/A
Ref.
A/D
IN/OUT
µ
P
Display
Keyboard
P.S.
+5V
-5V
+24V
The functional blocks of the instrument are as follows:
•
power supply
•
microprocessor (central unit + memory)
•
input circuit
•
LCD display
•
membrane keyboard
•
output circuit
4.1
Power supply
The instrument is powered if not otherwise specified with the order, by four internal batteries that can be
recharged through an external charger module supplied as a standard accessory.
The internal batteries are Ni-Cd rechargeable AA type with a nominal voltage of 1.25 V.
A section of the power supply circuit enables following voltages function :
+ 5 V logic and analog circuits
- 5 V analog circuits
A second section of the power supply circuit, configurated as a voltage multiplier generates a voltage
level of 24 V dc to interface a maximum resistance of 1000 ohm with a current simulation of 20mA.
4.2
Operative keyboard
The front panel is a tactile polycarbonate membrane keyboard, and has a working life of one million
operations per key.
The contact closure of the membrane keyboard keys is acknowledged as a coded signal by the
microprocessor which recognizes the operators instruction.
