The term "sample rate" refers to how many times a second an analog signal is "sampled" (sensed and converted to digital numbers--1's and 0's), then stored to memory.
Many of our chart recording products now have data acquisition capability (TA6000, TA11, Cobra 16 and -64, and WindoGraf). Besides the normal Thermal Array paper output, signal and event channel data can be stored and played back later on a PC for analysis, and then dropped into spreadsheets or documents for report generation. Cobra16, TA11, and TA6000 recorders allow this via the Memory Module option, and WindoGraf 930 and 980 models have it as standard. All of the above recording product lines use the sampling method of Samples Per Channel: The listed Sample Rate is captured simultaneously for each channel.
Most PC-based Data Acquisition products, such as Gould's Acquire 6600 and SmartCase 6600 sample using the Aggregate method: The sample rate is the addition of all storing channels added together. A TA11 will sample all channels simultaneously; the formula for calculating the total number of samples captured is: The number of channels stored x the selected Sample Rate x no. of seconds captured for = Total Samples. Our Acquire 6600 uses the Aggregate method (as virtually all PC-based data acquisition product do): The total number of samples / the no. of channels stored = the Sample Rate per channel. So with an Aggregate method, if the Sample Rate is stated as "30,000" and there are 3 channels currently being stored; then the sample rate per channel is actually "10,000". When shopping for Data Acquisition products, it is important to insure that the specifications of the product being considered can sample at the needed per channel rate; as most manufacturers do not mention that their maximum sample rate specification is actually stated in aggregate.
Maximum Sample Rate refers to how fast the Analog-To-Digital Converter (ADC) on the product can sample per second; Frequency Response is the actual limit in Hertz that the amplifier circuit can accurately measure. For instance: A TA11 8-channel recorder can sample at 250,000 samples per second, per channel (250ks/s, non-aggregate). The Basic DC Amplifier in the unit has a maximum Frequency Response of 25,000 Hz . This means that signals under 25kHz will pass through and be recorded accurately, but signals faster than that will likely not be captured. When trying to capture fast signals, a very high Sample Rate may not be the most important factor: The analog band-width (frequency response) must be high enough to allow the signal to pass through the "front-end" of the Amplifier before it can be digitally sampled. G.I.S. provides a large array of products that provide both high sample rate and fast band-width; giving the User a truly accurate representation of their captured signals.