Bandwidth – The signal frequency range that can pass through the analog input circuitry.
Effective Resolution – The measurement resolution of the module, taking into account both the resolution of the ADC and other factors such as quantization errors and RMS noise.
Gain Error – The degree to which the gain varies from the ideal, specified in percent or ppm of reading. This type of error is multiplied with the measurement.
Gain Error Drift – The amount that the gain drifts for every °C that the environmental temperature differs from the nominal temperature. For example, for an analog voltage input module, if the typical specification is at 25 °C, the gain error drift is 20 ppm/°C, and the environmental temperature is 27 °C, the additional gain error of the reading is 40 ppm.
Input Current Limit – The maximum amount of current that flows into the module based on limiting circuitry. Regardless of the amount of current supplied, it will be limited to a specified amount to prevent damage to the input.
Input Delay Time – The maximum amount of time required for an input signal to pass through the optical isolation circuitry of the module.
Input Impedance – The amount of resistance and reactance between a channel input and channel common. For example, if a module has an input impedance of 100 ohms, the resistance between channel input and channel common is 100 ohms.
LSB – least significant bit. The smallest detectable change in input value. This term is commonly used when determining offset.
For example, if a module has a resolution of 16 bits, an offset error of 6 LSB, and a ±15 V range,
Note: If the module has overranging, include the overrange in offset calculations.
Maximum Conversion Rate – The speed at which the module can update all of its output channels.
Maximum Working Voltage – The maximum voltage differential that can exist between any terminal on the terminal base and the ground in the backplane of the module (the network module ground level).
Noise – A measure of the amount of unwanted signal added by the analog output circuitry.
Nonlinearity – The amount of variance over the measurement range of the module.
Normal-Mode Rejection (NMR) – The degree of rejection in decibels (dB) of an undesired normal-mode noise voltage (often 50 or 60 Hz) on an input channel. Normal-mode rejection can be achieved by filters that reject 50 or 60 Hz signals, or by averaging to remove a broader range of frequencies.
Offset Error – The amount of additional voltage or current that can be introduced by the analog input circuitry. Offset error is added to measurements and is typically noted in least significant bits (LSBs) or in standard units.
Offset Error Drift – The amount that the offset drifts for every °C that the environmental temperature differs from the nominal temperature. For example, for an analog voltage input module, if the typical specification is at 25 °C, the offset error drift is 1 mV/°C, and the environmental temperature is 27 °C, the additional offset error of the reading is 2 mV.
Overcurrent Protection – Circuitry that protects the module from damage caused by current that exceeds the input range.
Overvoltage Protection – Circuitry that protects the module from damage caused by voltage that exceeds the input range.
Overranging – The ability to measure values beyond the nominal input range. Modules with overranging have the ability to measure a little more than the stated nominal range. For example, the [c]FP-AI-110 module has a ±60 mV range that can measure ±65 mV. The additional 5 mV is the overrange. When doing error calculations, use the entire range (including overrange) in the calculations. (Therefore, use ±65 mV for [c]FP-AI-110 offset and gain calculations).
ppm – parts per million. A measure of resolution. To convert a value in ppm to the corresponding unit, multiply the ppm by 10–6. For example,
2 ppm = 2 ´ 10
–6 = 0.000002
or 0.0002% of the whole. Therefore, 2 ppm of 5 V is 10 mV.
Relay Type – Relay types are single-pole single-throw (SPST), single-pole double-throw (SPDT), latching, and nonlatching. An SPST relay simply closes or opens a circuit. An SPDT relay switches a common (COM) terminal between a normally open (NO) and a normally closed (NC) terminal. Latching relays maintain their latest state even when powered down. Nonlatching relays return to their normally closed state when powered down.
Resolution – The number of bits that the analog-to-digital converter (ADC) uses to represent an analog signal. The higher the resolution, the greater the number of divisions the range is broken into, and therefore the smaller the detectable voltage change for a given input range and gain. Common resolutions for FieldPoint are 12 bits, giving 212, or 4096, divisions for the specified range, and 16 bits, giving 216, or 65,536, divisions.
Slew Rate – The maximum rate of change per unit of time for an analog output channel.
Transient Overvoltage – The highest voltage transient that can be input to the module for up to 60 seconds without affecting other modules on the bank.
Type of ADC – Different applications require different types of analog-to-digital converters (ADCs) for optimal performance. For example, an AC signal is usually best measured with a delta-sigma modulating ADC. Common types of ADCs include successive approximation, flash, half-flash, integrating, and delta-sigma modulating.
Update Rate – The speed at which the module reads all of its channels and updates its registers.