Fluke Victoreen 190, Руководство оператора

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Theory of Operation
General Circuit Description
2
2-1
Section 2
Theory of Operation
2.1 General Circuit Description
A block diagram of the circuit of the Model 190 is shown in Figure 2-1. The CMOS microprocessor is a TI
7000 series microprocessor, capable of addressing 64k bytes of memory. A 32k byte PROM contains the
operating program and an 8k byte RAM provides storage for operational and data logging information.
The microprocessor addresses the display via two display drivers. The microprocessor senses the
keypad directly, with the exception of the ON/OFF switch. The communications is direct from the
microprocessor through its ports, light emitting diodes, and photosensitive transistors. The
microprocessor reads and writes to both EEPROMs and reads count data directly from the probe adapter
module
A probe adapter module connection is provided on the back of the instrument. The probe adapter module
retains the calibration information for a specific probe and contains high voltage and threshold
adjustments for the probe. A portion of the circuit in the probe adapter module provides an adjustable
threshold for current drain through the detector. This circuit is used to detect a jam condition in the
detector and to signal the instrument. The pulse shaping circuit in the module accepts a wide range of
detector input amplitudes and pulse decay times.
Communication with the Model 190 is accomplished through an infrared two-way adapter that mounts at
the top of the instrument. The infrared receiver and transmitter are viewed through two small holes in the
upper edge of the decal covering the LCD.
2.2 Operational Considerations and Applications
Control and Configuration
The Model 190 makes use of two data bases for operation; one is stored in an EEPROM on the main
circuit board and one is stored in an EEPROM in the probe adapter module. The instrument EEPROM
determines which set of configuration and control data codes will be used to define the operating modes.
These codes may be user-modified with the optional Communicator (P/N 190-1A) to tailor the instrument
for a specific application.
For example, any or all of the front panel buttons may be disabled or the unit may be configured to
operate in only one Display Mode. Refer to the Instruction Manual provided with the Communicator for
further details.
Display Calculations
The Model 190 retains all data internally as both counts and counts per minute. All other displays are
calculated from these data sets and stored calibration information in the EEPROMS, allowing the operator
the capability to switch back and forth between the various display modes without affecting the database
used for calculations.