Data Acquisition

• Channel scalingThis automatically multiplies the value read by the fixed channel-scalingfactor.• Intrinsic functionsThese are mathematical functions applied to the data read, for example:• Inverse (1/x) of the data• Square root (√x) of the data• Natural logarithm (1n[x]) of the data• Base ten logarithm (log[x]) of the data• Absolute value [x] of the data• Square (x*x)• SpansThese allow sensors with linear calibrations to be converted to engineeringunits. The end points of the span are defined by the user and the linearcalculation of input signal values performed automatically. This is the sameas applying a first order polynomial y = a + bx to the input value x, and isparticularly suited for 4–20 mA current loops.• Polynomial equationsLinearization of non-linear data can be performed using the ‘n’ orderpolynomial equation shown in Appendix E.• Channel variable storageInternal variables are used for temporary storage of the readings taken fromone or more channel. These readings can then be added to the readings fromother channels or mathematical calculations applied before the data is logged,displayed, or returned to the host.• Mathematical and logical calculationsMathematical expressions containing arithmetic operators (+ = * / %),relational operators (< > < = etc), logical operators (AND, OR, XOR, NOT)and trigonometric functions (SIN, COS, TAN etc) can be applied to the valueread from the channel.A schedule is a list that tells the remote device which channel or number of channels datais to read, as well as the method by which the reading of data on each channel is to betriggered. When a trigger event occurs, all channels listed in the schedule are scanned,and depending on the type of schedule, the data logged, displayed or returned to the hostPC.Three different schedule triggers are typically defined:• Trigger by interval• Trigger on event• Trigger when condition is true