Measurement Computing Data Acquisition Systems rev.10.4 - Manual (Page 291)

Programmer’s Manual
908594
Daq API Command Reference 4.6-13
Option Type and Value Definitions Continued--DaqOptionType
WBK16 Options
Option Type
(optionType)
Description
Option Value
(optionValue)
Description
DcovWbk16X1_00 Sets PGA gain to: x 1.00
DcovWbk16X1_28 Sets PGA gain to: x 1.28
DcovWbk16X1_65 Sets PGA gain to: x 1.65
DcovWbk16X2_11 Sets PGA gain to: x 2.11
DcovWbk16X2_71 Sets PGA gain to: x 2.71
DcovWbk16X3_48 Sets PGA gain to: x 3.48
DcovWbk16X4_47 Sets PGA gain to: x 4.47
DcovWbk16X5_74 Sets PGA gain to: x 5.74
DcovWbk16X7_37 Sets PGA gain to: x 7.37
DcovWbk16X9_46 Sets PGA gain to: x 9.46
DcovWbk16X12_14 Sets PGA gain to: x 12.14
DcovWbk16X15_58 Sets PGA gain to: x 15.58
DcotWbk16PGA
Provides gain definitions
for the WBK16 PGA
(Programmable Gain
Amplifier)
See Note 1 regarding
Voltage Out & Total Gain.
DcovWbk16X20_00 Sets PGA gain to: x 20.00
DmotWbk16Immediate
Contains option value for
applying Excitation
Voltage. DmovWbk16ExcSrcApply
Applies the excitation source
voltage that is defined by
DcotWbk16ExcDac.
Note 1: V
OUT
= [(V
IN
x IAG) + DacOffset
SCALED
] x PGA
Where: V
OUT
is Voltage Out, and V
IN
is Voltage In
Note 2: Software Function for Dac Offset (Bridge Offset)
This note pertains to the DcotWbk16OffsetDac option type that is discussed in the preceding table. The Dac
Offset, also referred to as bridge offset, can be set to values in the range of -3.0 volts to +3.0 volts, divided by the
gain of the Instrumentation Amplifier (IAG). To do so, the following conversion is used:
Offset Value = [(Offset Voltage) x IAG x 682.5] + 2047.5
Where: Offset Value is a number in the range of 0.0 to 4095.0.
Example:
In this example we will determine the Offset Value; i.e., an integer in the range of 0 to 4095 that will give us a
desired offset of 0.25 volts. We will make use of the following considerations. Actual applications will vary,
accordingly.
• the Instrumentation Amplifier Gain (IAG) is set to x 10, i.e., DcovWbk16X10
• the desired Offset Voltage is 0.25 volts
Using the above equation we find that our offset value is 3754. The solution follows.
(0.25 x 10 x 682.5) + 2047.5 = 3754
Correlation of Offset Range with Instrumentation Amplifier Gain
IAG Value Allowable Range for Offset Voltage
x 1 ± 3.0 volts
x 10 ± 0.3 volts
x 100 ± 0.03 volts
x 1000 ± 0.003 volts