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ezeio2:expref:start [2020-09-18 19:11] – [Reverse expressions] andreh | ezeio2:expref:start [2022-11-16 23:33] – [Field expressions] andreh | ||
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===== Expressions ===== | ===== Expressions ===== | ||
- | {{indexmenu_n> | + | {{indexmenu_n> |
Within the configuration of an ezeio, mathematical expressions are used to produce a value/ | Within the configuration of an ezeio, mathematical expressions are used to produce a value/ | ||
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Enter the following in the " | Enter the following in the " | ||
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</ | </ | ||
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Since we are looking for kW-hours, we need to divide the momentary power with 36000 (3600 seconds in an hour, and we are re-evaluating 10 times per second). | Since we are looking for kW-hours, we need to divide the momentary power with 36000 (3600 seconds in an hour, and we are re-evaluating 10 times per second). | ||
+ | === Example: Signal filter === | ||
+ | |||
+ | If data from a register (or other field) includes a lot of noise and needs to be filtered over time, a simple field expression can be used to implement a IIR filter function: | ||
+ | |||
+ | <code javascript> | ||
+ | |||
+ | Knowing that the expression evaluated 10 times per second, we are keeping 99% of the value, and adding 1% from the signal every 100ms. Thus the response time for this filter is about 7s for a 3dB (50%) response. | ||
==== Reverse expressions ==== | ==== Reverse expressions ==== | ||