Spectrum M2p.59 Series, Hardware Manual, Page: 77 / 190

Analog Inputs Setting up the inputs
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To give you an example how the registers of the input range and the input offset are to be used, the following example shows a setup to
match all of the four signals in the second input offset figure to match the desired input range. Therefore every one of the four channels is set
to the input range of ± 1.0 V. After that the four offset settings are set exactly as the offsets to be compensated, but with the opposite sign.
The result is, that all four channels perfectly match the chosen input range.
Please note that this is a general example and the number of input channels may not match the number of channels of your card.
Input termination
All inputs of Spectrum’s analog boards can be terminated separately with 50 Ohm by software programming. If you do so, please make sure
that your signal source is able to deliver the higher output currents. If no termination is used, the inputs have an impedance of 1 Megaohm.
The following table shows the corresponding register to set the input termination.
M2p.591x Digital bandwidth filter
The cards of the M2p.591x series provide a digital (boxcar) bandwidth filter for enhancing the signal-to-noise ratio, which is enabled by
default. This reduces the available bandwidth digitally below the value otherwise defined by the anti-aliasing filter. In situations where the
full nyquist bandwidth is required or undersampling of the inputs is required (for the second nyquist zone), this feature can be disabled ma -
nually:
Because the digital bandwith filter of the M2p.591x cards does requires the generation of a higher internal
ADC sample rate, it is not available when using direct external clocking (clock mode SPC_CM_EXTERNAL).
Please see clock mode chapter for details.
Automatic on-board calibration of the offset and gain settings
All of the channels are calibrated in factory before the board is shipped. These values are stored in the on-board EEProm under the default
settings. If you have asymmetrical signals, you can adjust the offset easily with the corresponding registers of the inputs as shown before.
To start the automatic offset adjustment, simply write the register, mentioned in the following table.
Before you start an automatic offset adjustment make sure, that no signal is connected to any input. Leave
all the input connectors open and then start the adjustment. All the internal settings of the driver are changed,
while the automatic offset compensation is in progress.
As all settings are temporarily stored in the driver, the automatic adjustment will only affect these values. After exiting your program, all cali -
bration information will be lost. To give you a possibility to save your own settings, most Spectrum card have at least one set of user settings
spcm_dwSetParam_i32 (hDrv, SPC_AMP0 , 1000); // Set up channel0 to the range of ± 1.0 V
spcm_dwSetParam_i32 (hDrv, SPC_AMP1 , 1000); // Set up channel1 to the range of ± 1.0 V
spcm_dwSetParam_i32 (hDrv, SPC_AMP2 , 1000); // Set up channel2 to the range of ± 1.0 V
spcm_dwSetParam_i32 (hDrv, SPC_AMP3 , 1000); // Set up channel3 to the range of ± 1.0 V
spcm_dwSetParam_i32 (hDrv, SPC_OFFS0, -100); // Set the input offset to get the signal symmetrically to 0.0 V
spcm_dwSetParam_i32 (hDrv, SPC_OFFS1, -50);
spcm_dwSetParam_i32 (hDrv, SPC_OFFS2, 50);
spcm_dwSetParam_i32 (hDrv, SPC_OFFS3, 100);
Table 30: Spectrum API: register table for input termination settings
Register
SPC_50OHM0 30030 r/w A „1“ sets the 50 ohm termination for channel0. A „0“ sets the termination to1 MOhm.
SPC_50OHM1 30130 r/w A „1“ sets the 50 ohm termination for channel1. A „0“ sets the termination to1 MOhm.
SPC_50OHM2 30230 r/w A „1“ sets the 50 ohm termination for channel2. A „0“ sets the termination to1 MOhm.
SPC_50OHM3 30330 r/w A „1“ sets the 50 ohm termination for channel3. A „0“ sets the termination to1 MOhm.
SPC_50OHM4 30430 r/w A „1“ sets the 50 ohm termination for channel4. A „0“ sets the termination to1 MOhm.
SPC_50OHM5 30530 r/w A „1“ sets the 50 ohm termination for channel5. A „0“ sets the termination to1 MOhm.
SPC_50OHM6 30630 r/w A „1“ sets the 50 ohm termination for channel6. A „0“ sets the termination to1 MOhm.
SPC_50OHM7 30730 r/w A „1“ sets the 50 ohm termination for channel7. A „0“ sets the termination to1 MOhm.
Register Value Direction Description
SPC_DIGITALBWFILTER 100100 r/w A „1“ enables the digital BW filter, a „0“ disables it. As default the filter is active.
Register Value Direction Description
SPC_ADJ_AUTOADJ 50020 write Performs the automatic offset compensation in the driver either for all input ranges or only the actual.
ADJ_ALL 0 Automatic offset adjustment for all input ranges.