Introduction
The Rescale function, a math function, lets you multiply the amplitude of an acquired waveform by a constant or multiply by a constant and then add a constant. Additionally, the units of measure for the rescaled function can be converted to a wide variety of common units.
This function is used with special sensors or probes to obtain calibrated amplitude readouts in the units that match the sensor readings. It can also be used to switch between one system of units and another.
In the following tutorial you will use the rescale math function to convert a voltage reading to a current reading, remove a bias offset, and scale measurements.
Equipment Required
WaveSurfer MXsB Oscilloscope
Passive probe
Initial Setup
Displays shown in the tutorial are based on the following initial setup on a WaveSurfer MXsB oscilloscope:
 Connect a passive probe from Channel 1 to the CAL test point on the front panel. The CAL output is a 1 kHz square wave with an amplitude of 1 V
 Recall the default setup by choosing: File > Recall Setup > Recall Default.
 Turn off Channel 2.
 Auto Setup the scope: Press Auto Setup on the front panel. Select Confirm from the popup menu.
 Using the C1 dialog box, set the Channel 1 vertical scale to 200 mV/division and the vertical offset so that the bottom of the trace is one and one half divisions above the bottom of the display grid.
 Set the trigger level to 500 mV.
 This completes the initial setup. The scope display should be similar to Figure 1.
Using the Rescale Function
 We will rescale the waveform on Channel 1 to read the current into the probe tip. This is done by dividing the voltage waveform by the probe input resistance of 10 MOhms using the rescale math function.
 Open the Math dialog box by choosing: Math > Math Setup > .
 Select the source as Channel 1, the operator as rescale. Touch or click the Trace On box to display the trace.
 Touch or click on the Rescale tab on the right side of the math dialog.
 Double touch or click on the First Multiply By box. When the popup keypad appears, enter the number 100Exp 9 and press OK. This will cause all the samples in the channel 1 waveform to be multiplied by 1e7 (the same as dividing by 10 MOhms).
 Click or touch the Override Unit check box, a check mark will appear along with an Output Units box.
 Touch or click on the output units box. An onscreen keyboard will appear. Type in the units as A for Amperes, then, press OK. The units in the Math trace annotation box should change to nA.
The screen should appear as shown in Figure 2.
Supported Output Units abbreviations are as follows:
1. (blank)  No units 
21. L  Liter 
41. T  Tesla 
2. A  Ampere 
22. M  Meter 
42. UI  Unit interval 
3. C  Coulomb 
23. FT  Foot 
43. V  Volt 
4. CYCLE  Cycles 
24. IN  Inch 
44. VA  Volt amps 
5. DB  Decibel 
25. YARD  Yard 
45. W  Watt 
6. DBC  Decibel referred to carrier 
26. MILE  Mile 
46. WB  Weber 
7. DBM  Decibel Milliwatt 
27. N  Newton 
47. MIN  Min 
8. DBV  Decibel Volts 
28. OHM  Ohm 
48. HOUR  Hour 
9. DBUZ  Decibel Microamp 
29. PAL  Pascal 
49. DAY  Day 
10. DEC  Decade 
30. PCT  Percent 
50. WEEK  Week 
11. DIV  Divisions 
31. POISE  Poise 

12. Event  Events 
32. PPM  Parts per million 

13. F  Farad 
33. RAD  Radian 

14. G  Gram 
34. DEG  Degree (of arc) 

15. H  Henry 
35. MNT  Minute (of arc) 

16. HZ  Hertz 
36. SAMPLE  Sample 

17. J  Joule 
37. SWEEP  Sweeps 

18. K  Degree Kelvin 
38. SEC  Second (of arc) 

19. CEL  Degree Celsius 
39. S  Second 

20. FAR  Degree Fahrenheit 
40. SIE  Siemens 

You can also enter combinations of the above units following the SI rules:
 For the quotient of two units, use the character “/”
 For the product of two units, use the character “.”
 Exponents can be represented by a digit appended to the unit without a space
For example:
 Acceleration can be entered as M/S2 for meters per second squared
 Volts seconds can be entered as V.S.
In some cases, the units entered may be converted to simple units. For example entering V.A will display W (watts)
Continuing With the Tutorial
Save the Math trace to M1 (File pull down>Save Waveform>Save To Memory>Source Math>Destination M1>Save Now!).
Open the Math dialog box again. Define the Math trace to be the integral of M1. Turn on the Math trace.
The screen should appear as shown in Figure 3:
Because the trace M1 is unipolar positive, the integral produces a ramplike waveform as the positive mean value (as measured using the parameter P1) accumulates with time. If we want to see the integral of the waveform separate from the accumulating offset, we need to remove the mean value. We can do this by subtracting the mean value of the waveform. Use the Then Add field of the rescale function to add a constant. In our case the constant is the value of the mean multiplied by 1 in order to subtract it from the integral operation.
 Turn off the M1 trace and open the Math trace dialog box. Select the source to be C1 and the Operator to be Rescale.
 Touch or click on the Rescale tab on the right side of the Math dialog.
 Double touch or click on the First Multiply By box. When the pop up keypad appears, enter the number 100Exp 9 and press OK.
 Click or touch the Override Unit check box, a check mark will appear along with an Output Units box.
 Touch or click on the output units box. An onscreen keyboard will appear. Type in the units as A for Amperes, then, press OK. The units in the Math trace annotation box should change to nA.
 Measure the mean of the Math trace using P1 (Measure Pulldown>Measure SetupI>Show Table checked> Statistics On >P1 >Source Math>Measure Mean>).
 Using the Rescale tab in the Math setup dialog enter 1 times the mean value of the Math trace, as measured by P1, into the Then Add field. Save this waveform as M2 (File pull down>Save Waveform>Save To Memory>Source Math>Destination M2>Save Now!).
 Turn off the measurement parameters. Note that the mean value of the Math waveform is now at zero
 Select dual in the Math setup dialog. Select Operator2 to be integral.
The waveform should now appear as shown in Figure 4.
Note that the integral no longer increases with increasing time. The integral function also incorporates a rescale operation, and we could have done the same thing there. We chose to use the rescale function because it also offered the ability to redefine the units of the measurement. Note that the trace annotation box for the Math trace now lists the units as C for Coulombs. So once units are redefined subsequent math operations show the correct units of measure.
Conclusion
The rescale function allows us to scale waveforms by multiplying by a constant, and multiplying by a constant and then adding a constant. You can also use these functions to change the units of a trace or parameter .
This completes the tutorial.