Daqarta for DOS Contents
MUX CNFG' switch on your board. You can check the status of this switch by means of the information summary available via the ALT-H Plug-In Help system.
+/- 10 V +/- 5.0 V +/- 0.5 V +/- 50mV
external trigger. Make sure that whatever input you select is not the same bit as set for DDisk Remote or Averager Remote unless you are SURE you will not be using those options.
remote control to start and stop DDisk recording. Make sure this bit is not the same one used for Averager Remote or External Trigger.
remote control to start and stop the Averager. Make sure this bit is not the same one used for DDisk Remote or External Trigger.
Trigger Pulse source. Note that the STIM3 Stimulus Generator uses all 8 output bits if its DigOut is active, superceding any setting here. This is true even if the particular bit is itself inactive in the DigOut menu... the output is just left at zero. You can always set a bit of the DigOut output to function like the simpler Trigger Pulse output.
X-axis control menu. But by toggling the Pacer item from Timer to EXT, you select an EXTernal TTL clock signal as the source of the sample rate. You may toggle back and forth at any time during operation.
Few users will have need for the External Pacer mode, or have the special equipment needed to support it, but it offers very powerful benefits for certain applications. This mode allows the sample rate to be controlled externally, to provide exact synchronization to some external process. The external pacer signal may be fixed, or dynamically variable. For example, if you provide a sample clock that is synchronized to an engine or other machine's operating speed, you can view vibration spectra where each harmonic stays at the same screen location even as operating speed varies.
You must provide an external TTL clock signal at exactly the desired sample rate. Connect it to the "External Pacer" input (pin 26). (The DAS-20 documentation refers to this pin as "Cntr #1 Src / Ext Trig", but their usage of "trigger" varies... they really mean "pacer" here.)
Daqarta will make no attempt to determine the actual sample rate... X-axis markings and readouts will still be controlled by the normal X-axis menu, but they will have no effect upon the true sample rate. That's completely controlled by the TTL pacer signal you feed to the pin 26 input. You must insure that this never goes faster than the maximum sample rate (about 100 kHz), or you will get trashy data. (It will probably look like a version of the true waveform, with a forest of spikes growing out of it.)
However, the sample rate menu setting does affect certain other internal functions that deal with time units. When a Trigger Delay is set, the entered time value is converted internally to an equivalent number of sample periods. The delay operation is then carried out by counting samples. So if the true sample period is different from the setting, all trigger delays will be off by the same proportion. Dynamically changing the external sample clock will produce changing delays.
In RTime mode, Cycle times are handled just like Trigger Delay and will show the same sample clock effects. Sequential mode Cycle timing will be correct, since it is done with the system timer using absolute time, not sample counting. The Cycle adjustment control uses the same sample-period increment size in both RTime and Sequential modes, and is limited to a total of 32767 samples maximum, so the sample rate setting will affect both resolution and range.
If you use a varying External Pacer clock frequency during stimulus generation with the STIM3 Stimulus Generator or the Trigger Pulse option, the output frequencies will be scaled accordingly. The sample period established by the X-axis menu items will be used as the basis for STIM3 timing calculations, both for DAC sine waves and DigOut digital output pulses. All durations (Start, Rise, etc) are given in sample periods that may thus be variable in width.
DAS-20 .--------. Ch0 | 1 2 | Ch8, Ch0 Lo Ch1 | 3 4 | Ch9, Ch1 Lo Ch2 | 5 6 | Ch10, Ch2 Lo Ch3 | 7 8 | Ch11, Ch3 Lo Ch4 | 9 10 | Ch12, Ch4 Lo Ch5 | 11 12 | Ch13, Ch5 Lo Ch6 | 13 14 | Ch14, Ch6 Lo Ch7 | 15 16 | Ch15, Ch7 Lo Analog Gnd | 17 18 | Analog Gnd DAC 0 Out | 19 20 | DAC 1 Out Analog Gnd | 21 22 | Analog Gnd Digital Gnd | 23 24 | Digital Gnd Sample/Hold | 25 26 | External Pacer Cntr 1 Gate | 27 28 | Cntr 1 Out Cntr 2 Src | 29 30 | Cntr 2 Gate / Ext Int Cntr 2 Out | 31 32 | +5 Volts Digital Gnd | 33 34 | Digital Gnd Dig Out 0 | 35 36 | Dig Out 1 Dig Out 2 | 37 38 | Dig Out 3 Dig Out 4 | 39 40 | Dig Out 5 Dig Out 6 | 41 42 | Dig Out 7 Dig In 0 | 43 44 | Dig In 1 Dig In 2 | 45 46 | Dig In 3 Dig In 4 | 47 48 | Dig In 5 Dig In 6 | 49 50 | Dig In 7 `--------'
8-1-01 Bug Fix: When generating long stimulus bursts in RTime mode, hitting Pause caused sample overrun error. 3-1-01 Added support for STIM3A Dynamic Mode, update for Daqarta v2.00. 11-24-98 Bug Fix: If F:0 parameter was used to prevent Help File loading, then hitting ENTER from the ALT-H Help summary screen gave a blank screen instead of the proper 'Help file missing!" message. 8-18-98 Initial release.
Address Parameter A: AUTOEXEC.BAT ignored Averager Remote Control Bit Averager Remote Parameter Preset
DAC Output Range Digital I/O Preset DDisk Remote Control Bit DDisk Remote Parameter Preset DMA Level (D: Parameter)
Input Range Control Input Range Preset Parameter R: Introduction - DAS-20 Features IRQ (Interrupt Request) Parameter I:
Pacer, External Parameters, Configuration Parameter Overview Pinout, DAS-20 Connector Port I/O Preset Parameter P: Pulse Output Bit
Range Control Range Preset Parameter R: Remote Control Bit, Averager Remote Control Bit, DDisk Revision History
Trigger Pulse Output Bit Trigger, External Trigger, External Parameter Preset Trigger, Sweep vs Conversion Terminology
Questions? Comments? Contact us!We respond to ALL inquiries, typically within 24 hrs.
25 Years of Innovative Instrumentation
© Copyright 1999 - 2006 by Interstellar Research