Watlow Series 998 - Manual (Page 112)

Retransmit
Applications, Chapter 8 8.2 WATLOW Series 998 User’s Manual
Retransmit
When output 3 is ordered as a process retransmit output, channel A set
point or process value (input 1) or channel B set point or process value
(input 2) can be configured for retransmit. For accurate readings when
retransmitting to a chart recorder, the retransmit can be scaled and offset
separate from the input settings.
When model number 99 _ _-_ _ _ _-M _ _ _ is ordered, a process range of
0-20mA or 4-20mA can be selected at the [Prc3] prompt in the Output
Menu.
When model number 99 _ _-_ _ _ _-N _ _ _ is ordered, a process range of
0-5VÎ, 1-5VÎ or 0-10VÎ (dc) can be selected.
Here’s an example:
The Series 998 is controlling the temperature of a heat treat oven. The
temperature of the process must be recorded on a chart recorder. The
oven’s temperature operating range is from 600 to 900°F. The chart
recorder requires a 4-20mA signal.
To achieve this, set the following prompts in the Output Menu.
Set [Aout] to [PrcA] to identify the channel A process as the retransmit
variable.
Set [Prc3] to [`420] to select 4-20mA as the output signal.
Set [`ArL] to [`600] to set the retransmit signal low range at 600°F.
Set [`ArH] to [`900] to set the retransmit signal high range at 900°F.
Setting [ACAL] to [```0] assumes no calibration offset is required.
The retransmit output will be 4mA until the oven temperature reaches
600°F. Once it is above 600°F, the retransmit signal increases propor-
tionally to the temperature rise until it reaches 900°F. The retransmit sig-
nal will not exceed 4mA or 20mA.
Figure 8.2 -
Retransmit
Example.
Analog
Input 1
Control
Output 1A
Temperature
Tramsmitter
Heat Treat Oven
Heater
Chart Recorder
Control
Output 3
(4-20mA)
Power
Control
Device
TL W WA
PROCESS
1A 2A 1B 2B
CH A
CH B
DISPLAY
SERIES 998
MODE
AUTO
MAN
TL W WA
TL W WA
PROCESS
1A 2A 1B 2B
CH A
CH B
DISPLAY
SERIES 998
MODE
AUTO
MAN