====Rate====

This is a function of the [[class_LagCorrection|LagCorrection]] class.

===Description===

This function is used to calculate a [[lagged time]] based on a //rate//. 

Use this if the source of your lag is counting the **speed** or **rate** that your target is moving, instead of being measured with a **counter**. Note that in many industrial applications, field-based counters or totalisers are more accurate that performing calculations than rates are.

For example, you might have a conveyor system that has a speed measurement. If Sensor X is 50m away from Sensor Y, you can calculate the //time lag// between Y and X by going backwards and finding out how long it took for 50m of conveyor to pass.

===Parameters===

^Parameter^Type^Meaning^
|server|ARDI API Server|The ARDI server to query|
|query|string|The AQL Query to send|
|amount|float|The amount to lag the time by|
|origin|datetime|The ending/reference time (default=now)|
|seconds|int|The maximum number of seconds to search (default=1 day)|
|expected|int|The average amount of time in normal operation (default=10 minutes)|

===Returns===

The number of seconds of lag between the **origin** time and when **amount** has passed/flowed/been seen.

===Notes and Behaviour===

The **expected** time should be the maximum amount of lag you'd //expect// to have during normal operation (ie. if your machines didn't stop in the mean-time).

The **seconds** time should be the maximum amount of lag you're willing to search for.

===Example===

<code python>
    srv = ardiapi.Server('demo.optrix.com.au/s/pl')
    query = "'Paint Line' ASSET 'Distance' PROPERTY VALUES"
    lc = samplestream.LagCorrection()
    diff = lc.Amount(srv,query,25)
    print("Roller 2 Lag Correction - " + str(dt))
 </code>