An external timing potentiometer (pot) wired to remote adjust terminals can be used to adjust the time setting from a remote location; to extend the time range of the unit; or to act as a vernier control. Determining the resistance value of the unit’s internal pot is necessary for selecting the proper external pot. Calculate resistance value as follows:
- Determine time range of unit. example : 0.06 – 5 secs
- Determine from specifications the timing ramp (ohm/sec ratio) for that time range. The timing ramp is specified with the minimum time of the time range. example : 0.06 -100kohm/sec
- Multiply timing ramp by maximum time of time range. example : 100kohm/sec x 5 sec = 500kohm
- The product is the resistance value of the unit’s internal pot.
Remote adjustment is useful in applications requiring frequent time setting changes due to machine variations or changes in machine function. The external pot can be run from the control cabinet to the work station where time variations occur. Install external pot for remote adjustment as follows:
- Wire a remote pot of the same resistance value as the unit’s internal pot to the remote adjust terminals (remove jumper between terminals).
- Set unit’s internal pot at minimum setting. The remote pot will then provide the same time range as the unit.
The time range of a unit can be extended if an application occasionally requires a slightly longer time than the unit is capable of providing. This capability should be used for minimal time range extensions only. Install external pot for extending time range as follows:
- Wire a remote pot of the same resistance value as the unit’s internal pot to the remote adjust terminals.
- The internal and external pots are wired in series, so their resistance value is additive and provides an extended time range. Add time ranges of both pots to determine new time range.
| example: Time range of pots is | 0.06 – 5 secs. |
|---|---|
| Set internal pot at | 2 secs |
| Set external pot at | 5 secs |
| Total | 7 secs |
| Extended time range is | 2 – 7 seconds. |
Using an external pot as a vernier control provides fine adjustment of the time setting. Use in applications which require precise adjustment of slight changes in time setting. Install external pot for vernier control as follows:
- Determine time range of unit. example : 0.06 – 5 secs
- Determine range of variation in time setting.
example: If time setting will vary between 3 and 4 seconds, range of variation in time setting is 1 second: therefore, an external pot is used to make time adjustments within a 1 second time period. - Determine timing ramp for unit (see specifications) example : 100kohm/sec
- Multiply timing ramp by range of yariation in time setting. example : 100kohm/sec x 1 sec = 100kohm)
- The product is the resistance value of the external pot which will provide vernier control for a 1 second time period.
- Set unit’s internal pot for 3 seconds.
- Use external pot for adjusting time between 3 and 4 seconds.
