Limit value monitoring (Limit, Swap Limit) (0x382199, 0x302199)
You can define two limit values ("Limit 1" and "Limit 2") for the analog input. For each limit value, a variable of the same name in the process data indicates whether the current measured value is above or below the limit value.
Enabling limit value monitoring
In the factory setting, the limit value monitoring is disabled. To enable limit value monitoring, set the bits in the following indices to TRUE
- 0x80A0:07 "Enable Limit 1"
- 0x80A0:08. "Enable Limit 2"
Set limits
Use the indices to set the limits:
- 0x80A0:13 "Limit 1"
- 0x80A0:14 "Limit 2"
Invert limit function (Swap Limit)
The limit function can be inverted by enabling the "Swap Limit" bit in index
- 0x80A0:0E "Swap limit bits"
Limit value evaluation
If the limit values are exceeded or not reached, the bits in the indices 0x60n0:03 and 0x60n0:05 are set accordingly (see following table) and displayed via the process data.
The output in "Limit 1" (0x60A0:03) and Limit 2 (0x60A0:05) is displayed in 2-bit format:
"Swap Limit" = FALSE (Default) | "Swap Limit" = TRUE |
|---|---|
|
|
 | Limit evaluation The limit evaluation assumes a signed representation. The conversion to the desired presentation (index 0x80n0:02 'Presentation") only takes place after the limit evaluation. |
Example:
Specification: | |||
|---|---|---|---|
Presentation | Swap Limit | Limit 1 | Limit 2 |
Signed integer | FALSE (Default) | "Enable Limit 1" = TRUE | "Enable Limit 2" = TRUE |
"Limit 1" = 2.8 V Input "Limit 1" 0x80A0:13 | "Limit 2" = 7.4 V, Input "Limit 1" 0x80A0:14 | ||
Output: | ||
|---|---|---|
Input value | "Limit 1" (0x60A0:03) | "Limit 2" (0x60A0:05) |
1.8 V | 0x01hex, (limit value undershot) | 0x01hex, (limit value undershot) |
2.8 V | 0x03hex, (limit value reached) | 0x01hex, (limit value undershot) |
4.2 V | 0x02hex, (limit value exceeded) | 0x01hex, (limit value undershot) |
8.5 V | 0x02hex, (limit value exceeded) | 0x02hex, (limit value exceeded) |
| Linking in the PLC with 2-bit values The limit information consists of 2 bits. Limitn can be linked to the PLC in the System Manager. |
- PLC:
IEC61131-PLC contains no 2-bit data type that can be linked with this process data directly. To transmit the limit information, therefore, define an input byte (e.g. see Fig. Definition input byte ) and link the limit with the VariableSizeMismatch dialog.
