Instructions
UM-0085-B09 DT80 Range User Manual Page 43
RG
Order of Application
The DT80 applies channel options in a specific order, regardless of the order in which they are specified in a channel
definition. The channel option table below lists the channel options more or less in the order of application.
In general terms, the ordering is as follows:
1. First, the raw value is sampled, taking note of sampling options, i.e. those relating to the physical
measurement process. These include options in the input termination (
T, U) , input attenuator (A, NA),
resistance/ bridge wiring (
2W, 3W, 4W), gain lock (GL30V, GL3V, GL300MV, GL30MV) and excitation (I, II,
III, V, E, N) categories, along with NSHUNT, 2V, ESn and MDn.
The raw value may then be linearised according to the channel type, e.g. for thermocouples the appropriate
polynomial will be applied to convert millivolts into a temperature value (in the units specified by P36).
The resulting linearised value is then further processed as follows.
2. The channel factor is then applied, if specified. For most channel types this is a simple scaling (multiplier)
value.
3. A user specified scaling option – a span (Sn), polynomial (Yn), thermistor scaling (Tn) or intrinsic function (Fn)
– is then applied.
4. The resulting scaled and linearised value may then be manipulated using a data manipulation option –
difference (DF), time difference (DT), rate of change (RC), reading per time (RS) or integrate (IB).
5. A digital manipulation option for measuring the timing of signal transitions may then be applied (TRR, TRF,
TFR, TFF, TOR or TOF)
6. The data value processed up to this point may then be used as a reference value for other measurements (TR,
BR or TZ)
7. The data value may then be accumulated using one or more statistical options (each one in a separate option
set). Statistical channel options include AV, SD, MX, MN, TMX, TMN, DMX, DMN, IMX, IMN, INT, NUM and H
(histogram).
8. Finally, the resultant value after applying the above options (or values if multiple option sets are used) may be
stored in a channel variable using
=CV and op=CV options. Return, logging and/or display of the data may be
disabled using the
NR, NL, ND and W options, and output formatting can be specified using FFn, FEn and FMn
and "name~units".
Default Channel Options
All channel options have default values. The DT80 follows a 3-step procedure to determine what options to apply:
1. Start with the basic set of default options specified in the channel option table.
2. If the channel type specifies any default options then they are applied, overriding any conflicting basic default
options. Default options for each channel type are listed in the channel type table refer Table 3: DT80 Channel
Types (P37)
3. Finally, if an option is explicitly specified in the channel definition then that setting is used, overriding any default
setting. If more than one mutually exclusive option is specified then only the last one is used, e.g.
1V(AV,MX) is interpreted as 1V(MX). (If you want to output both the average and the maximum then use two
separate option sets, i.e.
1V(AV)(MX)).
For example, if you specify:
1R(4W)
then you are really specifying:
1R(U,NA,N,ES0,MD10,FF1,I,3W,4W)
In this case the basic default options are (U,NA,N,ES0,MD10,FF1). The R channel type specifies (I,3W) as its
default options, so the
(I) option (200µA excitation) overrides the (N) option (no excitation). Then the user specifies
(4W) which overrides the R channel type's default wiring option setting (3W).