SERVO
PRO NANOCHROME Gas Analyser
11
04416001A / Revision 7
1.3.5 Oven heater and control
Up to 6 ovens can be fitted into the main chassis. The temperature electronic
control hardware is mounted on the I/O board. There are 6 temperature control
loops (PID) in the software. The temperature is measured with a RTD. The
analogue to digital resolution uses 24 bit A/D converters. The heater is
controlled in a Pulse with Modulation (PWM) scheme.
There are 8 electronic relays mounted on the I/O board. These relays turn ON at
zero crossing voltage and turn OFF at zero crossing current thus eliminating
EMI. Oven circuits are also protected by a fuse mounted on the I/O board.
1.3.6 I/O board
The I/O board holds all the I/O functions of the instrument, shown in the table
below.
Table 1 : I/O board
All digital inputs and outputs, analogue inputs and outputs are transient and fuse
protected. The I/O board is connected to an external 40 pin I/O connector
through a flat cable connector
The 40 pin I/O connector mounted on the rear panel of the instrument may be
disconnected from the analyzer without the need to unscrew each wire
individually.
The I/O board holds the fuses for the I/O. Each fuse is socket mounted to make
replacement easy.
Digital I/O
Analogue I/O
❖
1 isolated digital input
❖
8 remote range dry contact outputs
❖
2 alarm dry contact outputs
❖
1 system status dry contact output
❖
1 extra relay
❖
10 G.C. valve contact outputs
❖
6 oven power relays
❖
6 oven temperature RTD input
❖
8 isolated process 4-20 mA output
