Instructions

UM-0085-B09 DT80 Range User Manual Page 77
RG
There may be fewer than expected samples in the first sample period after starting a schedule. This is because, by
default, schedule execution is synchronised to midnight (see Time Triggers — Synchronizing to Midnight (P60)) so a one
minute schedule will always execute on minute boundaries.
If insufficient statistical samples have been taken at the time when the report schedule runs then an error message
returned and the data value is flagged as "not yet set". The
SD and INT options require a minimum of two samples, the
others require at least one sample. To minimise the chance of this condition occurring:
• switch off the synchronise to midnight flag (/s), or
• ensure that the reporting schedule period is substantially longer than the statistical schedule period.
Statistical Functions
Average (AV)
The average or mean is the sum of all the channel readings divided by the number of readings. It is very useful in
reducing sensor noise.
Standard Deviation (SD)
Standard deviation is a measure of the variability of the data about the average or mean. The variation may be due to
electrical noise or process changes. The units of standard deviation are the same as the channel reading.
Maximum and Minimum (MX and MN)
The maximum and minimum of a set of channel readings can be reported with the MX and MN channel options.
The time at which these occurred can be reported with the TMX and TMN options, the date with DMX and DMN, and the
combined date/time ("instant") with the IMX and IMN channel options.
For example:
RS1M RA30M 1TK(AV) RB1D 1TK(MX)(TMX)(MN)(TMN)
1TK 24.2 degC
1TK 21.9 degC
1TK 19.0 degC
1TK 33.9 degC (Max)
1TK 15:10:00.000 (Tmx)
1TK 12.9 degC (Min)
1TK 04:33:00.000 (Tmn)
The above job measures the temperature once a minute (
RS1M). Every 30 minutes the average for the 30 minute period
is returned by the A schedule. Once a day (at midnight), the daily min/max temperatures are returned, along with the
times at which they occurred.
Integration (INT)
The integration channel option returns the integral (area under the curve) with respect to time in seconds using a
trapezoidal approximation. The units of an integration are those of the original reading multiplied by seconds.
In the following example a sensor returns a voltage that is proportional to the flow rate (0-1000mV = 0-0.2 l/s):
BEGIN
RS100T
S5=0,0.2,0,1000"litres"
1CV=0
RA2S 1V(S5,INT,+=1CV,W) 1CV("Fuel Used",FF3)
END
Fuel used 0.012 litres
Fuel used 0.104 litres
Every 100ms, the voltage output from the sensor is measured, scaled by span
S5 (yielding a value in litre/s) and the
integral is progressively accumulated (yielding a value in litres). This is then accumulated in
1CV (yielding the total
number of litres used since the schedule started), which is reported every 2 seconds.
The differences between the
INT and IB options (both of which calculate integrals):
• The
IB option uses two points only (the current value and the previous value) and calculates the area under the
curve using a single trapezoid. It does not involve the statistical schedule.
•
INT is a statistical option. It calculates the integral using a trapezoid for each sample point measured by the
statistical schedule.