MCE supports a number of different Item Types. Each Item Type is designed to simplify the processing of the most common types of raw data that are found in general everyday use. MCE process each type of data slightly differently and this article sets outs the differences.
For all Item Types, it is possible to set conversion to convert the raw values into different units. It is also possible to set calculations into the Item Types to change the behavior of the Item.
Absolute Item Type
This is the default type Item and is used for anything that is measured at a specific moment in time. Examples would include power, temperature, pressure, pH and many data points from telemetry/SCADA systems. Calculations that use an Absolute Item will only display data for the time in which there is an actual value. For any data gaps in the raw data then MCE will copy the last reading forward to fill in the gap and these points are deemed to be ‘interpolated’ and a specific flag is set for each point.
In the event that this method of filling in data gaps is not required then it is possible to set a calculation into the Item to change the underlying nature of the Item Type.
Consumption Item Type
This Item Type splits the value entered back over the number of Aggregation Period between the data and time of the value entered and the previous data point. This work well for chemicals and the like where a specific amount of chemical is used in a particular period of time.
Incrementing Item Type
This is a counting type Item where the reading will increase on a day to day basis. Eg A Flow meter or electricity meter etc. The system includes the provision to adjust for meters that lap. Calculation engine works out the difference between one reading and the previous reading and then splits the difference between the number of days in between the two readings.
Decrementing Item Type
This meter decreases on a daily basis.
Level Item Type
This Item is used if you wish to record the level in say an oil storage tank. The Level Item automatically takes the current level reading and subtracts it from the previous reading. Using a Unit Conversion it converts the difference into an actual consumption of oil for the period and then splits that consumption back over the period in question. (If the tank has a level scale of 0 to 100% and the tank is 4 m high and has a surface area of 10m2 then a change in level of 5% in the tank equates to 2m3 used in the period. To calculate this you will need to set up a Unit Conversion of 0.4 in the Meter i.e. every 1% change in the level equates to 0.4 m3 ).
If the Level Item notes that the current reading is greater than the previous reading it assumes that a delivery has been received during the period. For this period the Calculation Engine does not calculate any readings but instead estimates the consumption as being the average over daily use over the past three months. Level item works best with regularly entered Data.