Data Acquisition Systems and Instruments Specifications

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Data Acquisition Specifications

	Analog Input Channels:		This is the maximum number of analog channel inputs. The single-ended number is specified when single-ended inputs are available as twice the number of differential inputs. Differential channels use the difference between two signals as an input; common mode is filtered out. In some systems, differential inputs are combinations of two single-ended inputs. When this is the case, twice the number of differential channels are available as single-ended inputs.
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	Differential Channels		Differential channels have two inputs. The signal to process is the voltage (V) difference between the two inputs. For example, if one reading is 4.93 V and the other reading is 5.16 V, the meaningful value is the 0.23 V difference between the two. Often, this applies to precision measurements where the difference between two low-voltage inputs is small but critical.
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	Digital I/O Channels		Digital or discrete channels are used for low-level on-off signals used in applications such as communication, user interface, or control.
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	Sampling Frequency		Sampling frequency is the frequency of analog signal sampling and conversion to a digital value.
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	Resolution		Resolution refers to the degree of fineness of the digital word representing the analog value. A ten-bit number contains 210, or 1024, increments. A 0-10V signal could therefore be resolved into approximately 0.01V increments. A 12-bit representation would be in 212 (4096) increments, or divisions of 0.0024V for the same signal. Each additional bit doubles the resolution, and one bit is required for the polarity (sign) of a number.
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	Accuracy		Accuracy depends on the signal conditioning linearity, hysteresis, temperature considerations, etc. It is represented here as percent full scale of measurement range.
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	Datalogger / Recorder		Dataloggers and recorders combine instrument functionality with data storage capabilities. They may be designed for general-purpose use or specific applications.
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	Isolation
	Your choices are...
	Channel-to-Channel Isolation		The module channels are isolated from each other.
	Isolated Analog Voltage Input		The input voltage terminals are isolated.
	Isolated Analog Voltage Output		The output voltage terminals are isolated.
	Isolated Digital Input		The digital input voltage terminals are isolated.
	Isolated Digital Output		The digital output voltage terminals are isolated.
	Other		Other unlisted types of isolation.
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Application

	Application
	Your choices are...
	General Lab and Industrial		Products are designed for general laboratory and industrial data acquisition systems. Hardening against weather, shock, extreme heat, and other unusual conditions are not necessary.
	Environmental		Products are designed for use in environmental applications such as groundwater monitoring or pollution measurement.
	Vehicular		Products are designed for applications involving vehicular motion, and include provisions for factors such as high speed, shock, etc.
	Marine		Products are designed for use in water or salt water applications.
	Aerospace / Military		Products are designed for use in aviation, aerospace, or other military or defense applications, including associated technical or military standards.
	Seismic / Geotechnical		Products are designed for use in seismic applications such as earthquake or volcano research, or in industries such as mining.
	Weather / Meteorology		Products are designed to handle weather or atmospheric data, and may include weatherproofing.
	Medical / Biomedical		Products are designed for use in medical, biomedical, pharmaceutical, or surgical applications.
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Software

	Application Software Included?		Products include compatible software for control, or for monitoring data acquisition and signal conditioning from a supervisory or host computer.
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Memory and Storage

	RAM / On-board Memory:		Products use random access memory (RAM) or provide memory for control software or function/program loading.
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	Data Storage		Products have data storage capacity, typically with a hard drive.
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Network Specifications

	Networkable System?		Devices are designed to communicate with or be a node of a digital network.
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	Network Options:
	Your choices are...
	Ethernet		Ethernet is a local area network (LAN) protocol that uses a bus or star topology, and supports data transfer rates of 10 Mbps. The Ethernet specification served as the basis for the IEEE 802.3 standard, which specifies the physical and lower software layers. Ethernet uses the CSMA/CD access method to handle simultaneous demands. It is one of the most widely implemented LAN standards.
	Gigabit Ethernet		Gigabit Ethernet is a high-speed Ethernet standard from the IEEE 802.3z Gigabit Task Force.
	CANbus		CANbus is a high-speed serial data network engineered to exist in harsh electrical environments.
	DeviceNet		DeviceNet is a network designed to connect industrial devices such as limit switches, photoelectric cells, valve manifolds, motor starters, drives, and operator displays to PLCs and PCs. The network eliminates hard wiring while providing device-level diagnostics.
	SDS		Smart distributed system (SDS) is an advanced bus system for intelligent sensors and actuators using CAN-based technology.
	Foundation Fieldbus		Foundation Fieldbus is a bi-directional communications protocol used for communications among field instrumentation and control systems.
	PROFIBUS		PROFIBUS is a vendor-independent, open-field bus standard used in a wide variety of manufacturing and process automation applications.
	SERCOS		SERCOS (serial real-time communications system) is an open controller-to-intelligent digital drive interface specification. It is designed for high-speed serial communication of standardized, closed-loop data in real time, over a noise-immune fiber optic cable.
	Beckhoff I/O		Beckhoff I/O is a communications system that couples open fieldbus protocols to Beckhoff's bus terminal I/O. This allows connectivity to a large variety of devices on the bus terminal (K-bus).
	IEEE 1394 (FireWire®)		IEEE 1394 or FireWire® is an interface standard adopted by the Institute of Electrical and Electronics Engineers (IEEE) for very fast digital data transfers such as streaming video. IEEE 1394 connectors are used to transmit and receive data among FireWire devices, and are designed to replace external high-speed peripheral connections to personal computers, including hard disks, CD-ROMs, DVDs, graphics cards, high-speed scanners, direct video, monitors, etc. Tiny, robust FireWire connectors will also become important parts of home entertainment, communication, and appliance networks. FireWire is a registered trademark of Apple Computer, Inc.
	Other		Other unlisted or proprietary networks.
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Analog-to-Digital Conversion Type

	Analog-to-Digital Conversion Type
	Your choices are...
	Flash		Flash ADCs apply the input in parallel to many fast comparators whose thresholds are equally spaced throughout the desired input voltage range, typically 1V. At any moment, all the comparators that have thresholds below the input voltage are on, and the rest are off. A series of latching AND gates connect between adjacent comparators so that only the gate at the boundary between the on and off comparators is active. The input clock latches the AND gate outputs, and a pipelined circuit converts this one-out-of-N input to a binary output. Flash ADCs need 2N comparators to generate an N-bit output, and thus they tend to have no more than 6 to 10 output bits. Because the input has to drive all the comparators in parallel, the input capacitance is a major limitation to the bandwidth. The sampling bit synchronizer can often use this input capacitance as one element of the noise filter.
	Half-flash		Half-flash ADCs determine their output code by digitally combining the results of two sequentially performed, lower-resolution flash conversions.
	Integrator		Integrators are ADCs whose output code represents the average value of the input voltage over a given time interval.
	Delta Sigma (Modulator)		Delta sigma (modulator) is a high-accuracy circuit that samples at a higher rate and lower resolution than is needed and (by means of feedback loops) pushes the quantization noise above the frequency range of interest. This out-of-band noise is typically removed by digital filters.
	Successive Approximation		Successive approximation ADCs sequentially compare a series of binary-weighted values with an analog input to produce an output digital word in n steps, where n is the bit resolution of the ADC.
	Voltage-to-Frequency		Voltage-to-frequency ADCs convert an input voltage to an output pulse train with a frequency proportional to the input voltage. Output frequency is determined by counting pulses over a fixed time interval and the voltage is inferred from the known relationship. Voltage-to-frequency conversion has a high degree of noise rejection, because the input signal is effectively integrated over the counting interval. Voltage-to-frequency conversion is commonly used to convert slow and often noisy signals. It is also useful for remote sensing applications in noisy environments. The input voltage is converted to a frequency at the remote location and the digital pulse train is transmitted over a pair of wires to the counter. This eliminates the noise that can be introduced in the transmission of an analog signal over a long distance.
	Other		Other specialized or unlisted methods of analog-to-digital conversion.
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Filter Specifications

	Integral Filter?		Integral filters allow certain signal frequencies to pass while attenuating others. These filters can also operate on signal phase.
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	Filter Architecture:
	Your choices are...
	Analog (RC)		Analog filters are designed with resistors and capacitors. They are used for analog signals only, and are often used in low-noise requirement applications.
	Digital (FIR, IIR)		Digital filters are designed with solid-state components, and used for digital signals and quantized signals from a sample-and-hold amplifier. This category includes finite impulse response (FIR) and infinite impulse response (IIR) filters. Digital filtering can approach ideal bandpass characteristics.
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	Filter Function:
	Your choices are...
	Low Pass		Low pass filters block or attenuate signals at frequencies above the specified cutoff frequency.
	High Pass		High pass filters block or attenuate signals at frequencies below the specified cutoff frequency.
	Band Pass		Band pass filters block or attenuate signals at frequencies outside of the specified low pass and high pass cutoff frequencies. This is frequently done by combining or "cascading" low-pass and high-pass filters.
	Band Stop		Band stop filters block a portion of the frequency spectrum, allowing lower and higher frequencies to pass.
	All Pass		All-pass filters allow all frequencies to pass; they can be used to introduce desired phase shifts in signals.
	Other		Other unlisted or specialized filter forms.
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	Filter Type:
	Your choices are...
	Bessel		Bessel filters have a relatively flat bandpass and slow roll-off. The stopband is fairly monotonic (ripple-free). Their circuitry is complex compared to other filters.
	Butterworth		Butterworth filters provide a very flat response. There is almost no attenuation in the bandpass. The roll-off rate is somewhat slower than other filters.
	Cauer (Elliptic)		Cauer or elliptic filters provide the fastest roll-off for a given order (number of poles). The pass band and stop band will typically have ripples.
	Chebyshev		Chebyshev filters provide a very fast roll-off, but at the expense of a rippled pass band.
	Linear Phase		Linear phase response filters preserve the phase characteristics of a signal by time-delaying the signal components equally.
	Other		Other filter types.
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	Low Pass Cutoff Frequency		The low pass cutoff frequency is the nominal frequency below which the input signal is passed and above which the signal is blocked.
	Search Logic:		User may specify either, both, or neither of the "At Least" and "No More Than" values. Products returned as matches will meet all specified criteria.
	High Pass Cutoff Frequency		The high pass cutoff frequency is the nominal frequency above which the input signal is passed and below which the signal is blocked.
	Search Logic:		User may specify either, both, or neither of the "At Least" and "No More Than" values. Products returned as matches will meet all specified criteria.
	Number of Poles:		Poles are a measure of complexity of the filter circuitry. In general, more poles will provide a steeper roll-off for a given filter type.
	Your choices are...
	2
	4
	6
	8
	Other
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	Anti-aliasing Filter?		Aliasing is the misrepresentation of a signal that comes from an improperly slow sampling of a signal. An anti-aliasing filter generally has a sharper cutoff than a normal low-pass filter to reduce this misrepresentation due to the influence of frequencies higher than desired. It is specified according to the sampling rate of the system and there should be one filter per input signal.
	Search Logic:		"Required" and "Must Not Have" criteria limit returned matches as specified. Products with optional attributes will be returned for either choice.
	Programmable Filter?		Filter parameters such as cutoff frequencies may be interactively programmed by the user.
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Amplifier Specifications

	Integral Amplifier?		Amplifiers multiply a signal to the matching scale of the input device. Amplifier gains, or multiplication factors, may be greater than one or fractional for signal reduction.
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	Programmable Gain?		Amplifier gain may be adjusted according to the application needs. Adjustment may be from a local interface (such as a front panel) or from a computer interface.
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	Gain Range		Gain is the factor by which the input signal is multiplied. Gains are frequently greater than unity, but may be fractional when a reduction (attenuation) of signal amplitude is desired.
	Search Logic:		User may specify either, both, or neither of the limits in a "From - To" range; when both are specified, matching products will cover entire range. Products returned as matches will meet all specified criteria.
	Maximum Output		This is the limit of output voltage.
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	Bandwidth		Bandwidth is the difference between the high and low limits of the frequency response, typically defined by a variation from a nominal value by a stated value such as 3 dB.
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	Input Impedance		Impedance (Z) is the resistance to alternating signal flow and is a result of the resistance, capacitance, and the inductance of the circuitry of a device. Input impedance of an amplifier is the equivalent impedance that the signal input sees. Input impedance is typically specified to be much greater than the impedance of a sensor whose signal it is amplifying. Some applications, such as in the power and acoustic fields, require impedance matching of devices.
	Search Logic:		All matching products will have a value greater than or equal to the specified value.
	Common Mode Rejection Ratio:		The ability of an amplifier to obtain the difference between two inputs while rejecting the signal common to both is defined by the common mode rejection ratio (CMRR) and the common mode range. The simplest mathematical definition of CMRR is: CMRR = 20 log (differential gain / common mode gain)
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Environment

	Operating Temperature		Full required range of ambient operating temperature.
	Search Logic:		User may specify either, both, or neither of the limits in a "From - To" range; when both are specified, matching products will cover entire range. Products returned as matches will meet all specified criteria.
	Vibration Rating		Maximum vibration that the device can withstand and still meet performance specifications.
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	Shock Rating		Maximum shock that the device can withstand and still meet performance specifications.
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Form Factor

	Form Factor
	Your choices are...
	Panel / Chassis Mount		Devices attach to a panel or bolt onto a chassis.
	Modular Bay / Slot System		Devices stack in modular bays or slots, and can be interfaced to other units.
	Printed Circuit Board (PCB)		Devices are printed circuit boards (PCBs) that attach to enclosures or plug directly into computer backplanes.
	Rack Mount		Devices are rack-mounted and fit inside enclosures such as a standard 19 in. telecommunications rack.
	DIN Rail		Devices mount on a standard DIN rail. DIN is an acronym for Deutsches Institut für Normung (DIN), a German national organization for standardization.
	Stand Alone / Benchtop		Devices are benchtop or floor-standing units with a full casing or cabinet, and an integral interface.
	Other		Other unlisted form factors.
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Signal Inputs

	Your choices are...
	DC Voltage
	DC Current
	AC Voltage
	AC Current
	Frequency		Input for varying frequency, pulse, or other specialized waveform.
	Charge		Charge is the output of a piezoelectric device. A charge signal typically requires filtering and amplification.
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Sensor Inputs

	Your choices are...
	Accelerometer		The inputs are specifically for an accelerometer, such as a piezoelectric or current-fed sensor.
	Thermocouple		The inputs are for a thermocouple or thermocouple series.
	Thermistor		Inputs for thermistors and potentiometers handle variable resistance as a function of the process being measured.
	RTD		The inputs are designed for a resistance temperature detector (RTD).
	Strain Gauge / Bridge		The inputs are designed for a Wheatstone bridge, in full, half, or quarter bridge configurations. Strain gauges are sensors which commonly use Wheatstone bridges.
	LVDT / RVDT		The inputs are for a linear (LVDT) or rotary (RVDT) variable differential transformer.
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Specialized & Other Inputs

	Your choices are...
	Encoder		Inputs for an encoder signal such as binary, gray, or binary-coded decimal (BCD).
	Counter / Tachometer		Typically, the inputs from counters or tachometers are one signal per cycle counts.
	Timer / Clock		Inputs for any type of time signal.
	Relay / Switch		Inputs for a discrete, on/off signal from an exterior device.
	Other		Other unlisted or specialized inputs.
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Transducers & Excitation

	Voltage Excitation Supply?		Devices have a voltage output that is meant to power or activate the sensor whose signal the device is receiving.
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	Current Excitation Supply?		Devices have a current output that is meant to power or activate the sensor whose signal the device is receiving.
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Auxiliary Outputs

	Your choices are...
	Voltage Output		Variable voltage outputs such as 0-10V, ±5V, etc.
	Current Output		Variable current level outputs such as 0-20mA, 4-20 mA current loop, etc.
	Frequency Output		The output is a frequency or pulse signal such as amplitude modulation (AM), frequency modulation (FM), or pulse width modulation (PWM) or control.
	Timer / Counter Output		The output is a counting or timing of measured events.
	Relay Output		With switch-type outputs, the contacts are open or closed depending on the state of one or more of the inputs.
	Other		Other unlisted or specialized outputs.
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User Interface

	User Interface
	Your choices are...
	None		There is no user input or programmability. Instead, there is "black box" style of storage for download or processing elsewhere.
	Front Panel and Display		There are integral controls, a keypad, and/or a display on the panel of the unit.
	Touch Screen		The device's visual display screen is contact-sensitive to allow direct input.
	Hand-held / Remote Programmer		The interface unit is designed specifically to be held in the hand while the user enters program parameters, and may include remote programming.
	Computer Programmable		The device is interfaced to a separate supervisory or host computer.
	Other		Other unlisted user interface methods.
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Connection to Host

	Connection to Host
	Your choices are...
	USB		Universal serial bus (USB) is a 4-wire, 12-Mbps serial bus for low-to-medium speed peripheral device connections to personal computers (PC), including keyboards, mice, modems, printers, joysticks, audio functions, monitor controls, etc. The USB design is standardized by the USB Implementers Forum (USBIF), an organization that includes leading companies from the computer and electronics industries. The current USB specification is USB 2.0, which supports data transfer rates of up to 480 Mbps.
	IEEE 1394 (FireWire®)		IEEE 1394 or FireWire® is an interface standard adopted by the Institute of Electrical and Electronics Engineers (IEEE) for very fast digital data transfers such as streaming video. IEEE 1394 connectors are used to transmit and receive data among FireWire devices, and are designed to replace external high-speed peripheral connections to personal computers, including hard disks, CD-ROMs, DVDs, graphics cards, high-speed scanners, direct video, monitors, etc. Tiny, robust FireWire connectors will also become important parts of home entertainment, communication, and appliance networks. FireWire is a registered trademark of Apple Computer, Inc.
	GPIB		The general-purpose interface bus (GPIB) is designed to connect computers, peripherals, and laboratory instruments so that data and control information can pass between them. It was originally developed by Hewlett Packard (HP) and called the HPIB bus. GPIB is also known as the IEEE 488 bus, and is electrically equivalent to the IEC 625 bus.
	SCSI		Small computer systems interface (SCSI) is an intelligent I/O parallel peripheral bus with a standard, device-independent protocol that allows many peripheral devices to be connected to the SCSI port. A single SCSI bus can drive up to eight devices or units: the host adapter or controller, and seven other devices. Each device is assigned a different SCSI ID, ranging from 0 to 7.  SCSI formats include SCSI-1, SCSI-2, SCSI-3, Wide SCSI, Fast SCSI, Wide Fast SCSI, Ultra SCSI, Ultra2 SCSI, Ultra3 SCI (Ultra160), Ultra 320 SCSI, and Ultra640 SCSI.
	TTL		Transistor-transistor logic (TTL) is a common type of digital circuit in which the output is derived from two transistors. More commonly, however, TTL is used to designate any type of digital input or device.
	Parallel Interface		Parallel interface channels are capable of transferring more than one bit simultaneously. Parallel communications protocols include GPIB (IEEE-488, HPIB).
	Ethernet		Ethernet is a local area network (LAN) protocol that uses a bus or star typology and supports data transfer rates of 10 Mbps. The Ethernet specification is the basis for the IEEE 802.3 standard, which specifies the physical and lower software layers. To handle simultaneous demands, Ethernet uses carrier sense multiple access/collision detection (CSMA/CD) to monitor network traffic.
	Modem		Modems (modulator-demodulators) are devices or programs that enable a computer to transmit data over telephone lines. Computer information is stored digitally, whereas information transmitted over telephone lines is sent in the form of analog waves. A modem converts between these two forms.
	Radio / Telemetry		Communication from the data acquisition device to a host or storage unit is achieved via radio transmission.
	Other		Other unlisted, specialized, or proprietary communication configurations.
	Direct Backplane Interface		The circuit board installs directly into a computer motherboard or backplane.
	RS232/422/485		RS232/422/485 is an interface between data terminal equipment (DTE) and data communications equipment (DCE) employing serial binary data interchange.
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	Transmission Rate		Transmission speed in bits per second.
	Search Logic:		All matching products will have a value greater than or equal to the specified value.
	Web Enabled?		The device contains hardware and software protocols such as hypertext transfer protocol (http) or Web access protocol (WAP) for being addressable to, or a node of, the World Wide Web for remote monitoring or communication.
	Search Logic:		"Required" and "Must Not Have" criteria limit returned matches as specified. Products with optional attributes will be returned for either choice.

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