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

For DI-1110, DI-1120, DI-2008, DI-2108, DI-2108-P, DI-4108, and DI-4208 devices, use channel 8 for digital inputs, channel 9 for rate, and channel 10 for a 16-bit counter.

For DI-1110, DI-1120, DI-2008, DI-2108, DI-2108-P, DI-4108, and DI-4208 devices, rate channel 9, the upper byte of the diff field specifies a moving-window filter length for rate computation, from 0 for noisy and responsive to 63 for smooth and delayed (resulting in filter lengths 1 through 64).

To specify channels on multiple DI-1100, DI-1110, DI-1120, DI-2008, DI-2108, DI-2108-P, DI-4108, and DI-4208 devices, to each channel index (0-10) add 16 times the number of devices with lower serial numbers or listed ahead of it in the argument to di_open. The channels for each device must grouped together, with all channels for each device at indices greater than those for the previous device and less than those for the next device listed adjacent to it in the argument to di_open, or the default order (for DeviceDriver = "DI360NT.DLL" by decreasing model number, then within each model) by increasing serial number. For DI-2008 if any device has more than one analog channel enabled or all DI-2108-P, the number of enabled channels on each connected device must be identical or 0.

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 on the input list?

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 a voltage channel

diff = 1 for a thermocouple channel

diff = 0 (reserved for compatibility - these instruments are always single-ended)

diff = 0 (these instruments are always differential)

diff = 0 (these instruments are always differential)

For DI-1110, DI-1120, DI-2008, DI-2108, DI-2108-P, DI-4108, and DI-4208 rate channel 9, the upper byte of the diff field specifies a moving-window filter length for rate computation, from 0 for noisy and responsive to 63 for smooth and delayed (resulting in filter lengths 1 through 64). For DI-2008, diff = 1 specifies a thermocouple instead of voltage channel.

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 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 channels 1 through 8 and 17 through 24 of DI-500-16 and DI-510-48 instruments. When channel 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 channel 1 is configured for differential operation, channel 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.

dig_out_enable = 0 (reserved for compatibility).

When dig_out_enable is 1, digital output is enabled and the data appearing on the digital output bits is written to lines D0 through D4 of the digital output port.

When dig_out_enable is 0, digital output is disabled. When digital output is disabled and:

chan = 0 to 15, digital output bits D2 through D0 are used to specify an acquisition method (either average, minimum, or maximum. Refer to the description of dig_out for full details). In other words, you cannot use the three least significant bits of digital output, they are used to specify acquisition method.

chan is on a multiplexer, lines D3 through D0 of the digital output port are set to the least significant four bits of the EXP board input being multiplexed, and dig_out_enable automatically becomes enabled (chan setting of 16 or greater automatically overrides a dig_out_enable = 0 setting). In other words, with a MUX channel, you cannot use the four least significant bits of digital output (they are used) and you cannot specify a maximum or minimum acquisition method.

When dig_out_enable is 1, digital output is enabled and the data appearing on the digital output bits is written to lines D0 through D3 of the EXPANSION port.

When dig_out_enable is 0, digital output is disabled. When digital output is disabled and chan is on a multiplexer, lines D3 through D0 of the EXPANSION port are set to the least significant four bits of the channel to which the multiplexer is connected, and dig_out_enable automatically becomes enabled (when chan is on a multiplexer, a dig_out_enable = 0 setting is automatically overridden). In other words, with a MUX channel you cannot use the four least significant bits of digital output, they are taken.

dig_out = 0 (reserved for compatibility).

When digital output is enabled (dig_out_enable = 1), the digital out bits output a digital value to lines D4 through D0 of the digital output port. When digital output is disabled (dig_out_enable = 0) and chan = 0 to 15, digital out bits D2 through D0 are used to specify an acquisition method:

	D2	D1	D0
	0	0	0	reports average value
	0	0	1	reports maximum value
	0	1	0	reports minimum value

All Dataq Instruments hardware products continuously sample data using a burst sampling technique. With the burst sampling technique, the board or hardware device samples data at one rate (referred to as the maximum sampling rate or burst rate) while your computer reports (i.e., displays and stores) this data at another rate (called the sample rate or throughput rate). Again, the burst rate determines how fast the board or hardware device samples your data and the sample rate determines how fast the sampled data is reported. The board or hardware device can sample data much faster than it can report it. For example, let’s say we want to record one channel of data at 100 Hz and our burst rate is set at 50kHz. In this example, we will be sampling the data at 50kHz and reporting it at 100Hz, a 500 to 1 ratio. This means that for every 500 data points sampled, only 1 will be reported. The dilemma becomes: which data point out of the 500 gets reported? Fortunately, you have a choice of methods for reporting this single data point: Averaging Acquisition MethodThis method averages all of the data points in the burst sample and returns this average as the single value for storage and display. This is the most universal method and should be used in all cases unless you wish to report peak or valley values (in which case you would use the maximum or minimum method respectively)., Maximum Acquisition MethodThis method returns the highest value data point in the burst sample for storage and display. The rest of the data points in the burst sample are ignored., Minimum Acquisition MethodThis method returns the lowest value data point in the burst sample for storage and display. The rest of the data points in the burst sample are ignored., and Last Point Acquisition MethodThis method simply returns the last input data point in the burst sample for storage and display. The rest of the data points in the burst sample are ignored. This is the only data reporting method used by DI-700 instruments..

When digital output is disabled (dig_out_enable = 0) and chan is on a multiplexer, dig_out bits D3 through D0 are set to the least significant four bits of the EXP board input being multiplexed. In other words, with a MUX channel you cannot use the four least significant bits of digital output, they are taken.

When digital output is enabled (dig_out_enable = 1), the digital out bits output a digital value to lines D3 through D0 of the EXPANSION port.

When digital output is disabled (dig_out_enable = 0), there is no digital output (digital output is disabled). However, when digital output is disabled and chan is on a multiplexer, lines D3 through D0 of the EXPANSION port are set to the least significant four bits of the channel to which the multiplexer is connected, and dig_out_enable automatically becomes enabled (when chan is on a multiplexer, a dig_out_enable = 0 setting is automatically overridden). In other words, with a MUX channel you cannot use digital output, it is disabled.

The Last Point Acquisition MethodThis method simply returns the last input data point in the burst sample for storage and display. The rest of the data points in the burst sample are ignored. This is the only data reporting method used by DI-700 instruments. is enabled.

The Averaging Acquisition MethodThis method averages all of the data points in the burst sample and returns this average as the single value for storage and display. This is the most universal method and should be used in all cases unless you wish to report peak or valley values (in which case you would use the maximum or minimum method respectively). is enabled. It is suggested that you set ave = 1 (also set dig_out_enable = 0 and dig_out = 0) for these instruments to allow for future programming enhancements.

Digital output bit D4 and ave work together to specify the acquisition method.

	D4	ave	Acquisition Method
	0	0	Last Point Acquisition MethodThis method simply returns the last input data point in the burst sample for storage and display. The rest of the data points in the burst sample are ignored. This is the only data reporting method used by DI-700 instruments.
	0	1	Averaging Acquisition MethodThis method averages all of the data points in the burst sample and returns this average as the single value for storage and display. This is the most universal method and should be used in all cases unless you wish to report peak or valley values (in which case you would use the maximum or minimum method respectively).
	1	0	Minimum Acquisition MethodThis method returns the lowest value data point in the burst sample for storage and display. The rest of the data points in the burst sample are ignored.
	1	1	Maximum Acquisition MethodThis method returns the highest value data point in the burst sample for storage and display. The rest of the data points in the burst sample are ignored.