Campbell Scientific CR1000KD CR800 and CR850 Measurement and Control Systems - Page 264

Section 7. Installation CRBasic Example 61. PT100 in Four‐Wire Full‐Bridge 'See FIGURE. PT100 in Four-Wire Full-Bridge (p. 263) for wiring diagram. Public BrFullOut Public Rs_Ro Public Deg_C BeginProg Scan(1,Sec,0,0) 'BrFull(Dst,Reps,Range,DfChan,Vx1,MPS,Ex,RevEx,RevDf,Settle,Integ,Mult,Offset) BrFull(BrFullOut,1,mV25,1,Vx1,1,2500,True,True,0,250,.001,.02344) 'BrTrans = Rf*(X/(1-X)) Rs_Ro = 50 * (BrFullOut/(1 - BrFullOut)) 'PRTCalc(Destination,Reps,Source,PRTType,Mult,Offset) PRTCalc(Deg_C,1,Rs_Ro,2,1.0,0) NextScan EndProg 7.8.19 Running Average The AvgRun() instruction calculates a running average of a measurement or calculated value. A running average is the average of the last N values where N is the number of values, as expressed in figure Running-Average Equation (p. 264), Figure 82: Running-average equation where XN is the most recent value of the source variable and XN-1 is the previous value (X1 is the oldest value included in the average, i.e., N-1 values back from the most recent). NANs are ignored in the processing of AvgRun() unless all values in the population are NAN. AvgRun() uses high-precision math, so a 32-bit extension of the mantissa is saved and used internally resulting in 56 bits of precision. Note This instruction should not normally be inserted within a For/Next construct with the Source and Destination parameters indexed and Reps set to 1. Doing so will perform a single running average, using the values of the different elements of the array, instead of performing an independent running average on each element of the array. The results will be a running average of a spatial average of the various source array elements. A running average is a digital low-pass filter; its output is attenuated as a function of frequency, and its output is delayed in time. The amounts of attenuation and phase shift (time delay) depend on the frequency of the input signal and the time length (which is related to the number of points) of the running average. 264