Omega CL526 Manuale Utente
13
4
FUNCTIONAL DESCRIPTION
The CL526 portable calibrator block diagram is shown below.
Microprocessor
D/A
(converter)
Keyboard
Gain Control
Comparator
and buffer
IN/OUT
Switch
Reference
junction
Power supply
Display
Converters for
backligh
A
Digital
interface
interface
Signal OUT
output signal
output signal
IN/OUT terminals
Rj signals
A
Ni-MH
Batteries
External battery
charger
•
power supply
•
microprocessor (central unit + memory)
•
input circuit
•
cold junction compensator (Rj)
•
LCD display
•
operative keyboard
•
digital to analog converter
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-MH rechargeable AA type with a nominal voltage of 1.25 V. The jumper “J1” (mounted on
the mother board), when soldered into the “B” position, allows the instrument to be powered by the four internal
rechargeable batteries or, if needed, directly from the power line. The voltage of the four batteries in series
(approximately 5V) is connected to the input of a hybrid circuit.
Pressing the <ON> key will provide the two levels of voltage for the circuitry of the instrument:
through an external charger module supplied as a standard accessory.
The internal batteries are Ni-MH rechargeable AA type with a nominal voltage of 1.25 V. The jumper “J1” (mounted on
the mother board), when soldered into the “B” position, allows the instrument to be powered by the four internal
rechargeable batteries or, if needed, directly from the power line. The voltage of the four batteries in series
(approximately 5V) is connected to the input of a hybrid circuit.
Pressing the <ON> key will provide the two levels of voltage for the circuitry of the instrument:
+ 5 V for logic and analog circuits
- 5 V for analog circuits
- 5 V for analog circuits
The second section, on the power supply circuit, is configured as a voltage multiplier generating for the final output stage,
a voltage of 24V dc. The above voltage levels are required to work with an external resistance of 1000
a voltage of 24V dc. The above voltage levels are required to work with an external resistance of 1000
Ω
maximum when
in current simulation mode (20 mA - 20 V). During operative modes, other than current simulation a diode de-energizes
the hybrid circuit reducing the overall power consumption.
Recommendations and instructions to convert the instrument for a power supply with normal alkaline batteries are
described in par. 8.3.
the hybrid circuit reducing the overall power consumption.
Recommendations and instructions to convert the instrument for a power supply with normal alkaline batteries are
described in par. 8.3.
4.2
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 is acknowledged as a coded signal by the microprocessor that
recognizes the operators instructions.
Keys are interconnected on a 4x3 matrix; the microprocessor identifies directly the active key.
The values of the <▲
The contact closure of the membrane keyboard is acknowledged as a coded signal by the microprocessor that
recognizes the operators instructions.
Keys are interconnected on a 4x3 matrix; the microprocessor identifies directly the active key.
The values of the <▲
▲
▲
▲>
and <▼
▼
▼
▼>
keys (membrane slidewires) are acknowledged through the converters built in the
microprocessor chip.