Front Panel Operations
Setting Operating Conditions
2
2-23
Setting the Mx+B Scaling
Perform the procedure in Figure 2-14 to set the Mx+B scaling for any configured
channel. In preparation, the instrument must be in the inactive mode (not scanning or
monitoring) and the desired channel must be configured with a measurement function
(see Figures 2-4 to 2-9) and selected (see Figure 2-3). To exit at any time, press the C
key; however, any Mx+B parameters previously entered will remain. Scaling allows a
measurement value (x) to be modified with a fixed multiplier (M) and a fixed offset (B).
A channel with scaling other than the default of 1x+0 will display Mx+B when the
channel is selected. When scaling is used, only a number is displayed; function
identifiers such as ºC, Hz, Ω, VAC, and VDC are removed. If the results from Mx+B
scaling are nonsense, double check the signs and multiplier values for M and B.
Examples
Multiplier. If a pressure transducer provides 100 mV for 100 PSI, 200mV dc for 200
PSI, etc., the instrument would read directly in PSI with a multiplier of 1000, or M=+1k
and B=000.00. For example, a PSI of 156.98 would display the number 156.98.
Offset. If you are monitoring line voltage of 115V ac and you want the instrument to
display the variations above and below 115V ac instead of the actual voltage, the
instrument would display the differences by subtracting -115 from the measurements, or
B=-115.00 (M=1.0). For example, 117.21V ac would display only the number 2.21;
113.45V ac would display the number -1.55.
Multiplier and Offset. If the instrument is measuring temperature using the ºF scale, but
you want it to display the measurements in ºC, the conversion formula ºC=5/9(ºF-32),
rewritten in decimal ºC=.55555ºF-17.777, could make the conversion with M=+.55555
(entered as +555.55m) and B=-017.78. For example, 72.2 ºF would display the number
22.28.
Restrictions
Linearity. The transfer characteristic of the transducers or measurement modifications
must be linear, with fixed multipliers (M) and fixed offsets (B).
Overload (OL) Display. The decimal point location and scaling (m, X1, k, M) selected
for the "B" value determines the scaling for the result. For example, if B=xxx.xx x1, the
result will range over ±999.99 only. Anything greater than +999.99 or less than -999.99
will show "OL" (overload).
Clearing Mx+B Scaling from a Channel
To clear Mx+B parameters from a channel, the Mx+B parameters can be programmed to
1x+0 (M=1, B=0), or the channel function can be changed to any other selection,
including OFF.