Syntax

With 16 channels or less: chan = (channel # - 1).

With more than 16 channels: chan = (channel # - 1) + 32 (mux letter - "A" +1)

channel# is the analog input channel you wish to sample. On instruments with more than 16 channels, mux letter is the letter you assigned to the instrument (written on the overlay) during installation and initial configuration. This letter is important for keeping track of all the analog input channels on your instrument(s). For example, let’s say we have three DI-760-32 instruments multiplexed together and we want to record analog input channel five on the third instrument. What channel do we specify for chan? During installation, you would have labeled the instruments "A" "B" and "C." From the equation:

chan = (channel# - 1) + 32(mux letter - "A" + 1)

chan = (5 - 1) + 32(C - A + 1)

chan = 4 + 32(2 + 1)

chan = 4 + 96

chan = 100

With 16 channels or less: chan = channel #

With more than 16 channels: chan = channel # mod 16 + 16(output channel +1)

channel# is the analog input channel on the EXP board you wish to sample. output channel is the position of the jumper on the EXP board. On hardware with more than 16 channels, the mod operator in the equation above combines two integer expressions using modulo arithmetic. For two integer values, modulo arithmetic returns only the remainder from an integer division. That is, 6 mod 4 is 2, the remainder of the integer division of 6 by 4. For example, let’s say we have three 32-channel EXP boards multiplexed to a DI-220 Series board and we want to record analog input channel five on the third EXP board. What channel do we specify for chan?

On each EXP board, each bank of 16 analog inputs is multiplexed into one output (specified by the position of the OUTPUT CHANNEL jumper on the EXP board). This output from the EXP board is connected to an internal analog input on the DI-220 Series board. Assuming the first EXP board uses output channels 0 and 1 and the second EXP board uses outputs 2 and 3, the third EXP board will multiplex inputs 0 through 15 into output channel 4 and inputs 16 through 31 into output channel 5.

chan = (channel#) mod 16 + 16(output channel +1)

chan = (5) mod 16 + 16(4 + 1)

chan = 5 + 80

chan = 85

 

Now suppose we want to record channel 23 on the third EXP board. What channel do we specify for chan in this case?

chan = (channel#) mod 16 + 16(output channel +1)

chan = (23) mod 16 + 16(5 + 1)

chan = 7 + 96

chan = 103

 

Finally, suppose we have just one DI-220 Series board (not multiplexed) and we want to record channel 6. What channel do we specify for chan? Since we are using non-multiplexed hardware (only 16 channels), the first equation applies.

chan = channel#

chan = 6

diff = 0 for single ended input configuration.

diff = 1 for differential input configuration (do not set diff = 1 for channels on multiplexers, even though the inputs are differential).

diff = 0 (DI-730 instruments are always differential).

diff = 0 for single ended input configuration.

diff = 1 for differential input configuration.

This configuration allows you to see the difference between 2 differential input channels, but only on chan 1 through 8 and 17 through 24 of DI-500-16 and DI-510-48 instruments. When chan 1 through 8 or 17 through 24 is specified for differential operation, the other channel that creates the differential pair is automatically selected, eight channels away. For example, if chan 1 is configured for differential operation, chan 9 becomes the companion channel, similarly with 2 and 10, 8 and 16, 18 and 26, etc. In every case, the lowest channel number becomes the positive (+) differential input and the automatically selected channel becomes the negative (-) differential input.

Reserved for compatibility.