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Bad Value Hold

Function Overview​

Bad Value Hold is an essential feature of industrial IoT gateways, designed to guarantee continuous and reliable data collection. After users add specific collection points to the bad value hold list, if data acquisition fails due to communication disconnection, device fault or other abnormalities, the gateway will automatically retain the last valid normal value collected for this point. This prevents system misjudgment or operation interruption caused by missing or abnormal data.

Function Configuration​

Bad Value Hold belongs to data processing functions. When data collection fails, the last successfully collected data value will be maintained.

1.Add Bad-Value-Hold data point

Figure 1 Add Bad-Value-Hold data point

2.Save Configuration

Exception handling: The method for handling abnormal data when the gateway is offline or communication is interrupted. There are two options: using the last good value and using a default value.

Keep Good Quality Stamp on Exception: Whether the quality stamp of the data remains "Good" when an exception occurs.

Exception default value: When an exception occurs, the data point is assigned the configured default value.

Figure 2 Add data point

Data Simulation: Use Modbus Slave to simulate ModbusTCP data collection, then add the collected points to the bad value hold list;

Point Configuration: Set Keep Good Quality Stamp on Exception to false, then check the value and status of MQTT subscribed data;

# Data Subscription: Add data points to the real-time data publishing topic via MQTT, and subscribe to MQTT messages to monitor data changes;

: when, MQTT valueandstatusvalueas follows.

Status:Good；value:2


Figure 3 Keep Good Quality Stamp = False (Normal Collection Status)

Point Configuration: Set Keep Good Quality Stamp on Exception to false.;

Observation: The values and status of MQTT-subscribed data when data collection is disconnected are shown in the figure below;

Status:Error；value:2


Figure 4 Keep Good Quality Stamp = False (Collection Disconnected)-

Point Configuration: Set Keep Good Quality Stamp on Exception to false.;

Observation: The data values and status subscribed via MQTT during normal data acquisition are shown in the figure below;

Status:Good；value:2


Figure 5 Keep Good Quality Stamp = True (Normal Collection Status)

Point Configuration: Set Keep Good Quality Stamp on Exception to false.;

Observation: The values and status of MQTT-subscribed data when data collection is disconnected are shown in the figure below;

Status:Good；value:2


Figure 6 Keep Good Quality Stamp = True (Collection Disconnected)