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Dynamic Variables

Path: Objects > TestServer > Dynamic

13 variables whose values change over time. These are essential for testing subscriptions, monitored items, and data change notifications.

All dynamic variables are read-only.

Variable Reference

Counters

BrowseName DataType Update Interval Behavior
Counter UInt32 1 second Increments by 1 every second. Starts at 0.
FastCounter UInt32 100 ms Increments by 1 every 100ms. Starts at 0.
SlowCounter UInt32 10 seconds Increments by 1 every 10 seconds. Starts at 0.

Testing notes:

  • FastCounter is ideal for testing subscription sampling intervals
  • Create a subscription with 200ms publishing interval, monitor FastCounter -- you should see every other update
  • SlowCounter is useful for testing longer publishing intervals and keep-alive

Random Values

BrowseName DataType Update Interval Behavior
Random Double 500 ms Random value in [0.0, 1.0)
RandomInt Int32 1 second Random integer in [-1000, 1000]
RandomString String 2 seconds Random alphanumeric string, 8-24 characters

Testing notes:

  • Every data change notification should have a different value
  • Useful for testing deadband filtering (set a deadband on Random and verify fewer notifications)

Waveforms

BrowseName DataType Period Formula
SineWave Double 10 seconds sin(2 * PI * t / 10) -- smooth oscillation between -1 and 1
SawTooth Double 5 seconds (t % 5) / 5 -- linear ramp from 0 to 1, then resets
Square Boolean 2 seconds true for 1s, false for 1s, repeating
TriangleWave Double 8 seconds Linear ramp from -1 to 1 to -1, period 8s

Testing notes:

  • Waveforms are computed on every read (no timer), so they are always current
  • SineWave is good for testing analog deadband filtering
  • Square is good for testing boolean data change detection

Timestamps

BrowseName DataType Behavior
Timestamp DateTime Returns the current server time on every read

Testing notes:

  • The value changes on every single read, making it ideal for verifying that your client receives fresh timestamps
  • Source timestamp in the DataValue should closely match the value itself

Status Cycling

BrowseName DataType Update Interval Behavior
StatusVariable StatusCode 3 seconds Cycles through: Good -> BadCommunicationError -> UncertainLastUsableValue -> repeat

Testing notes:

  • Verify your client correctly interprets different status code classes:
    • Good (0x00xxxxxx)
    • Bad (0x80xxxxxx) -- indicates an error
    • Uncertain (0x40xxxxxx) -- value may not be reliable
  • Test data change filtering with status change triggers

Nullable Value

BrowseName DataType Update Interval Behavior
NullableDouble Double 4 seconds Alternates between a valid Double value (StatusCode = Good) and StatusCode = BadNoData

Testing notes:

  • When status is Good: value is a random double in [0, 100)
  • When status is BadNoData: value is 0 but should be treated as unavailable
  • Tests how your client handles variables that intermittently have no data

Subscription Testing Guide

Basic subscription

  1. Create a subscription with publishingInterval = 1000 (1 second)
  2. Add Counter as a monitored item with samplingInterval = 1000
  3. Expect one data change notification per second, values incrementing by 1

Fast sampling

  1. Create a subscription with publishingInterval = 200
  2. Monitor FastCounter with samplingInterval = 100
  3. Expect ~5 notifications per second

Deadband filtering

  1. Monitor SineWave with an absolute deadband of 0.5
  2. Notifications should only arrive when the value changes by more than 0.5
  3. With a period of 10s and deadband of 0.5, expect ~4 notifications per period

Status change trigger

  1. Monitor StatusVariable with DataChangeTrigger = StatusValue (trigger on status or value change)
  2. Expect notification every 3 seconds as the status cycles
  3. Change to DataChangeTrigger = Status to only trigger on status changes