Operating Description
A master 4 to 20mA signal is fed into a USC to set the required speed rate from 0 to 100%
The USC will measure the speed of the motor via a proximity sensor on the output shaft. The speed range on the output shaft is 0 to 5Hz.
The difference between the master speed setting and the actual speed is calculated and saved in Mem6 as a percent deviation signal (Dev%).
- When the absolute deviation is less than the LowDev (low deviation) both the RLY1 RLY2 will be off.
- When a positive deviation is greater than LowDev and less than HiDev (high deviation) then the "Faster" relay (RLY1) with switch on an off using the programmable settings On_Time and Off_Time.
- When positive deviation is greater than HiDev then the "Faster" relay (RLY1) with switch on continuously.
- When a negative deviation is less than LowDev and greater than HiDev then the "Slower" relay (RLY2) with switch on an off using the programmable settings On_Time and Off_Time.
- When a negative deviation is less than HiDev (high deviation) then the "Slower" relay (RLY2) with switch on continuously.
Declarations
Variables To Change User Function
| Description | Constant | Label | Value |
|---|---|---|---|
| Low Deviation in percent | Con_a | Low Dev% | (5) 1 to 5 |
| Relay on time (seconds) | Con_b | On time | (0.1) 0.1 to 0.5 |
| Relay Off Time (seconds) | Con_c | Off_Time | (2) 0.5 to 2 |
| Hi Deviation in percent | Con_g | Hi Dev% | (10) 5 to 20 |
Variables Required For Equation
| Description | Constant | Label | Value |
|---|---|---|---|
| Equation time correction | Con_d | EqTimCor | 10 |
| Counter value | Con_e | EqCntVal | -1 |
| Initialise value | Con_f | EqIntVal | 0.0 |
| On time counter | Mem4 | OnTimCnt | |
| Off time counter | Mem5 | OfTimCnt | |
| Deviation | Mem6 | Dev% |
At power on both relays are off and OnTimCnt and OfTimCnt both contain the value of 0
If OnTimCnt is = 0 then the deviation signal is read to determine if the up or the down relay should be switched on.
USC Programs
| File | Comment |
|---|---|
 Help |
If unexpected results occur when loading the .usc file press back and click on help for instructions. |
 UAP00181.usc |
First Issue. |
| UAP00182.usc |
Convert to USC config 105 standard. |