What is the difference between an analog and digital signal?
An analog signal is infinitely continuous; a digital signal is quantized or broken up depending on bit resolution.
Why is it important to ensure a higher sampling rate than the bandwidth, or rate of change, of my application?
It is important to sample faster than the rate of change in an application to ensure sample cycles are available to capture important moments in the application.
How many force sensors can be connected to a signal conditioner?
This is dependent on the sensor’s output impedance of excitation circuitry. The parallel combination of resistive loads cannot be less than the minimum required load for the instrument supply as found on the instrument spec sheet.
What is a bit?
A bit of information is either and “on” or “off” state and is represented by the number 1 for on and 0 for off. Each bit has two states which makes 3 bits equal to 2^3 or 8 combinations.
What is bit resolution?
The smallest step amount assigned to a bit combination and can be found by dividing the load amount the bits are spread over by the number of combinations from bits available.
What are “nibbles”, “bytes” and “words”?
A nibble = 4 bits, and byte = 8 bits and a word = 16 bits.
What does “kilo”, “mega” and “giga” mean in the digital domain?
Kilo is 1024, mega = 1024^2 , giga = 1024^3. Therefore 8kbytes means that we have 8 x 1024 = 8192 pieces of 8 bit information.
What is analog to digital conversion (ADC conversion)?
This is the process in which an analog signal is quantized into a digital signal. Usually performed by a device known as an analog to digital converter, or ADC.
What is sampling rate?
The number of times per second an analog to digital converter takes a reading and converts the reading into a number for use with digital system.
What is the Nyquist criteria?
In order to properly re-create an analog signal, the sampling rate must be at least twice the frequency of the source analog signal to ensure all prevalent information is captured.
Is sampling rate affected by electrical loads, such as impedance of a force sensor?
Typically, no however in some multiplexed system sampling rate is divided equally among different channels.
What is bandwidth?
The span of input frequencies that a device is designed to operate within.
Why do I sometimes see a –3db cutoff frequency listed as a specification, what does that mean?
This is the point where a signal will reduce in attenuation to about 70.7% of the original signal due to the component configuration in items such as a filter or amplifier.
What is Output and Input Impedance?
Output impedance is the minimum resistive load able to be seen by an instrument’s output that will not cause a voltage drop in the instruments voltage output or the maximum resistive load able to be seen by an instrument’s current output without causing a drop in current. Input impedance is the amount of resistive loading able to be seen by an instruments electrical input. Instrumentation typically has very high input impedance to reduce resistive errors.
What does filter settling time mean?
If an instrument is subjected to an impulse signal, settling time is the time from peak value to zero value in the output signal.