Omega Multifunction Indicator-Simulator, CL526 manual Functional Description, Power supply

4 FUNCTIONAL DESCRIPTION

The CL526 portable calibrator block diagram is shown below.

	External battery	Ni-MH
	charger	Batteries
A	Converters for	Power supply	Reference
	backligh		junction
			Rj signals
	Display		Digital
			interface
	A
	D/A	Microprocessor	Keyboard
	(converter)
	Signal OUT
	output signal	Comparator	output signal
	Gain Control		IN/OUT
		and buffer
			Switch
			IN/OUT terminals

•power supply

•microprocessor (central unit + memory)

•input circuit

•cold junction compensator (Rj)

•LCD display

•operative keyboard

•digital to analog converter

4.1Power 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:

+5 V for logic and 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 1000Ω 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.

4.2Keyboard

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 <▲> and <▼> keys (membrane slidewires) are acknowledged through the converters built in the microprocessor chip.

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