Alarm limits on a reading — a conductivity too high, a tank too low. Limits raise alarms whenever a reading crosses them, whether or not any control mode uses it, and they can also hold modes off as interlocks.
Open the device from Devices, then Limits.
Limits are set on Modbus probes only, for now. IO-Link sensors have no Limits row on the screen, and the app cannot set limits yet. For an IO-Link level sensor, use its tank settings: their low and low-low levels work as interlocks.
| Tier | Alarm | Severity |
|---|---|---|
| Low-low | 312 Low-Low | Severe |
| Low | 310 Low | Warning |
| High | 311 High | Warning |
| High-high | 313 High-High | Severe |
Each tier is independent — set only the ones that matter. The values must rise in order: low-low < low < high < high-high, among the tiers switched on.
Corrosion readings offer high and high-high only. A corrosion rate is never too low, so a CR-300’s corrosion readings have no low tiers. (Upcoming firmware.)
PTSA (Pyxis ST-500) opens at low-low 50, low 75, high 125, high-high 150 ppb, still off until you switch each one on. (Upcoming firmware.)
A limit alarm names the sensor, for example Inhibitor Level Low-Low in the alarm list, and Inhibitor Level reads 0.12, below the configured low-low limit in its message. The alarm detail keeps the tier as its title, with the sensor on the line below. See Labeling a level probe. (Upcoming firmware; earlier firmware shows only the tier, such as Low-Low.)
The deadband stops a reading that hovers at a limit from raising and clearing the alarm over and over. The alarm raises when the reading crosses the limit and clears only once it has come back by the deadband.
Every tier you switch on can also be picked as an interlock — hold the chemical pump off while the tank is low-low. A limit is then the one threshold for both the alarm and the interlock, so the two can never disagree.
Limits on Modbus probes as interlocks are new in an upcoming firmware update. Earlier firmware offers only IO-Link sensor limits; Modbus probe limits raise alarms but do not stop a mode.
Tank levels have their own settings. For a level sensor, the low and low-low levels are set in its tank settings: for an IO-Link sensor they are written into the sensor itself — see Tank settings — and for a Pyxis LS-200/202 they set the Level reading’s limits — see Modbus Probes.