SM 04L01A01-01E
1-1
1
PRINCIPLE OF OPERATION
1.1 Block diagram of the DX/1.2 Input section
Chapter 1 Principles of Operation
This chapter describes the principles of operation for the DX100 and DX200.
1.1 Block Diagram of the DX
Data storage functions
Input section
Calculation function
Alarm function
Communication function
(optional)
Input terminal
Scanner assembly
A/D assembly
CPU
External storage
Internal memory
Display unit
Remote function
Relay contact
(optional)
Transmitter power supply
(optional)
Figure 1 Block diagram
For datails see schematic diagram page 6-1 and 6-2.
1.2 Input Section
1.2.1 A/D Assembly
The A/D assembly has items such as a programmable gain amp, voltage reference,
PWM modulator, current source for RTD measurements, differential amp, voltage source
for RJC, serial parallel converter, control logic, and an occurred scanner SSR control
signal.
The A/D assembly uses a sinewave oscillating type self-resonant switching power supply
(DC/DC converter), and noise filtering is achieved by signal integration.
The A/D assembly detects the frequency of the power while it is ON and the integrated
time becomes 20 ms or 16.67 ms. Therefore it carries a very high rate of noise rejection
for the power frequency (in auto mode).
In case the power frequency of the instrument and of the measured object are different,
the appropriate integrated time is manually selectable. In case of the DX106, DX112,
DX210, DX220, or DX230, the selection of 100 ms for 50/60 Hz is also available. A 16 bit
resolution is achieved regardless of the integrated time.
1.2.2 Input Terminal
The input terminal is removable. The internal printboard is isothermal because a print
board with a metal core is being used. Therefore, stable reference junction
compensation is realized.