Instruction Manual

4.0 ANALOG INPUTS

Connecting analog signals to the ANAFAZE 8 PID is normally straightforward. Most

signals, including thermocouples can be directly connected and mixed in any order.

However, some problems may occur that could reduce accuracy and possibly damage

the unit. Sections 4.1 through 4.4 indicate some of the potential areas for concern.

[See

typical input DIAGRAM in section 4.13]

4.1 COMMON MODE VOLTAGE

Common mode voltage is the voltage between the ground at the sensor and the ground at

the ANAFAZE 8 PID. It can be an AC or DC voltage and appears equally at the high

and low input terminals. Frequently it is caused by large currents flowing in the ground

path between the ANAFAZE 8 PID and the sensors. The effects are minimized by

locating the ANAFAZE 8 PID as close as possible to the sensors. Do not exceed the

maximum common mode voltage of 125 volts AC.

4.2 NORMAL MODE VOLTAGE

Normal mode voltage appears across the terminals of the input and is the signal from the

sensor plus any undesirable noise. The major cause of this noise is AC power line pick-

up. The effects are reduced by the ANAFAZE 8 PID's capacity to integrate the signal

over a multiple of the power line frequency. Further reduction can be achieved by

locating the ANAFAZE 8 PID near the sensors and by using twisted and shielded sensor

wires. Do not exceed the maximum normal mode voltage of 2 millivolts.

4.3 GROUNDING

For best accuracy, observe the grounding recommendations for connecting each input

and output signal. The analog signal grounds should be connected to the ground

terminals on the analog input terminals. The communication and control outputs should

also be connected with their respective grounds. Do not mix the grounds or connect them

together. The analog input section is optically isolated from the processing and control

section. Connecting the grounds together will negate this feature and could damage the

unit. If possible, route the analog signal cables separately from the communication,

control and power cables.

4.4 SOURCE IMPEDANCE

Each sensor has a certain output impedance which is effectively connected across the

ANAFAZE 8 PID input amplifier when a measurement is made. To reach the rated

accuracy, the maximum source impedance should be 20 ohms. Consult ANAFAZE for

operation with higher source impedance.