Multifunction Analog Input/Output USB Data Acquisition Products

Select from a large assortment of 16, 32, 64, 96, and 128-channel multifunction analog input modules. Analog inputs are available as either single-ended or differential. Choose from either 12 or 16-bit versions with speeds up 500kHz. All models incorporate two 16-bit analog outputs, 16 lines of digital I/O, and are integrated inside a rugged, small sized steel enclosure with an anti-skid bottom. A DIN rail mounting provision is available for installation in industrial environments. Additional features include software autocalibration (real-time) and on-board references for increased accuracy. Extended temperature (-40 to +85C) is available.

Analog input boards are useful for measuring variably changing conditions in the real world. When we want to measure these variably changing conditions, we need analog inputs to convert these changing real world conditions to changing electrical quantities. For example, monitoring the temperature inside a wood kiln, or the water pressure on the output of a pump, or the heart rate of a medical patient. In each of these cases, you can use one of our analog input devices to convert the electrical data from a sensor or transducer into binary data that can then be used by your computer. The device that converts this data is known as an analog to digital converter (abbreviated ADC, A/D, or A to D). An analog input is a measurable electrical signal with a defined range. The analog input changes continuously in a definable manner in relation to the measured property. This data is very useful for process monitoring, process control, or simple monitoring / data collection and acquisition. ACCES' analog input boards amplify and multiplex input signals from thermocouples, strain gauges, accelerometers, photo sensors, flowmeters, RTDs, thermistors, voltage sources, millivolt sources, and current sources, just to name a few.

There are basically three types of analog input signals used to measure these conditions. They are voltage, current, and resistance.

Voltage Mode Connections...

If voltage mode is used, analog input connections can be either single-ended or differential. Low per-channel cost is a major advantage of using single-ended inputs because only one multiplexer switch is needed per channel and there is less system wiring. Single-ended inputs all share a common return or ground line. The measurement is the difference between the signal and the ground. Only the "high" signal wires are connected through the amplifier and multiplexer. The "low" wires return through the system ground connections. That is, both the signal source and the amplifier are referenced to ground. This arrangement works fine as long as the ground potential difference is very small. However, if there is a large difference in ground potential, extraneous currents can flow and generate errors. This is called a "ground loop". Ground potential differences (ground loops) can cause larger interference problems than electromagnetic fields. Ground loops occur if the sensors are tied to a local ground. That local ground can be many volts different from the ground potential at the receiving circuit. Single-ended measurements are also more susceptible to noise than differential measurements due to differences in the signal paths and the tendency to pick up surrounding electrical activity. With single-ended inputs you have no way of distinguishing between the signal and the noise.

Illustration of one singled-ended input circuit

To avoid this problem, a differential-input connection can be used with an amplifier that has a high common mode rejection ratio. A differential arrangement connects both ends of the signal source to the inverting and non-inverting inputs of the amplifier. Measurement is the difference in voltage between the input and the reference, which helps to reduce noise and any voltage that is common to both wires. Twisting wires together will ensure that any noise picked up will be the same for each wire. In this way, voltage due to ground loops appears as a common mode voltage and can be rejected by the common-mode-rejection properties of the amplifier. An instrumentation type amplifier (rather than a simple operational amplifier) is required and two multiplexer switches are required per channel. An obvious disadvantage of differential inputs is that you need twice as many wires, so you can connect only half the number of signals, compared to single-ended inputs.

Illustration of one differential input circuit

If you have signals larger than 1V, short signal wires, and close together signal sources, single-ended inputs should be fine. If your application falls outside these boundaries, differential inputs would be the wise choice.

Current Mode Signal Connections (e.g. 4-20 mA or 10-50mA inputs)...

In industrial applications, where wiring can be very long, it is common to use "current transmitters"; i.e., devices located at or near the transducer which convert the sensor output to an analog current signal (e.g. 4 to 20 mA). Current signals are sometimes used because they are relatively immune to errors such as induced noise and voltage drops due to lead resistance. and have become a de facto standard for critical process control measurements. Another plus is that it saves money due to reduced wiring cost. Current mode operation is somewhat susceptible to magnetically-induced errors. The simplest solution is to use twisted-pair signal lines and to keep those lines remote from power lines or other sources of magnetic induction. Also, at the receiving circuit, the signal usually must be converted into a voltage and level-shifted to a zero-based range so that it can be digitized using the full input capability of the digitizer.

Resistance Mode Connections...

Resistance measurement is most commonly associated with direct inputs from temperature sensing devices, such as thermistors and resistance temperature detectors (RTDs). RTDs are temperature sensors that exploit the predictable change in electrical resistance of some materials with changing temperature. They are slowly replacing the use of thermocouples in many industrial applications below 600C, due to higher accuracy and repeatability. Thermistors are widely used as inrush current limiters, temperature sensors, self-resetting overcurrent protectors, and self-regulating heating elements. Thermistors differ from RTDs in that the material used in a thermistor is generally a ceramic or polymer, while RTDs use pure metals. The temperature response is also different; RTDs are useful over larger temperature ranges, while thermistors typically achieve a higher precision within a limited temperature range (usually -90C to 130C).

Signal Conditioning...

Signal conditioning is an essential requirement in many applications and systems which demand accurate and precise measurements. Signal conditioning circuits convert one type of electronic signal into another type of signal that can be used to improve and enhance the data acquisition system and application. Sometimes the data acquisition card that you plug into the computer provides necessary conditioning; sometimes that signal conditioning must be done external to the computer. In general, signal conditioning consists of amplification, isolation, filtering, sensor excitation, cold-junction compensation and more.

Signal inputs accepted by our signal conditioners include DC voltage/current and AC voltage/current. Sensor inputs can be accelerometer, thermocouple, thermistor, resistance thermometer (RTDs), strain gauge or bridge, and LVDT/RVDTs. Signal conditioned outputs include voltage, current, frequency, relay, isolation, and more.

Illustration of a complete analog input data acquisition system

ACCES offers a wide variety of external signal conditioning products which include analog, digital, and serial signal conditioning. Sometimes the data acquisition product you plug into the computer provides the necessary conditioning; and sometimes that signal conditioning must be done external to the computer.

Click the following wikipedia links to learn more about analog inputs, signal conditioning and data acquisition in general.

12 or 16-Bit Multifunction Analog Input/Output USB DAQ Products
Products # Inputs Res BIP RG Uni RG Gain Speed FIFO AutoCal On-Board # Outputs Res Dig I/O XT
USBP-II8IDO4ATwo A/D inputs16n/a1 (0-5)n/a4 KHz peakNono calNo8 In/4 SSR OutYes
USB-AIO16-16A16 SE, 8 DIF1644Software500kHz*YesYes21616 I/OYes
USB-AIO16-16E16 SE, 8 DIF1644Software250kHz*NoYes21616 I/OYes
USB-AI16-16A16 SE, 8 DIF1644Software500kHz*YesYes16 I/OYes
USB-AI16-16E16 SE, 8 DIF1644Software250kHz*NoYes16 I/OYes
USB-AIO12-16A16 SE, 8 DIF1244Software500kHz*YesYes21616 I/OYes
USB-AIO12-1616 SE, 8 DIF1244Software250kHz*NoYes21616 I/OYes
USB-AIO12-16E16 SE, 8 DIF1244Software100kHz*NoNo21616 I/OYes
USB-AI12-16A16 SE, 8 DIF1244Software500kHz*YesYes16 I/OYes
USB-AI12-1616 SE, 8 DIF1244Software250kHz*NoYes16 I/OYes
USB-AI12-16E16 SE, 8 DIF1244Software100kHz*NoNo16 I/OYes
RES = resolution   BIP RG = bipolar ranges   Uni RG = unipolar ranges | * = Yes, FIFO

DAQ-PACK Multifunction 64-Channel Count Economy Analog Input/Output USB Products
Products # Inputs Res BIP RG Uni RG Gain Speed FIFO AutoCal On-Board # Outputs Res Dig I/O XT
DPK-AIO16-64MA64 SE, 32 DIF16 44Software500kHz*YesYes21616 I/OYes
DPK-AIO16-64ME64 SE, 32 DIF16 44Software250kHz*NoYes21616 I/OYes
DPK-AI16-64MA64 SE, 32 DIF16 44Software500kHz*YesYes16 I/OYes
DPK-AI16-64ME64 SE, 32 DIF16 44Software250kHz*NoYes16 I/OYes
DPK-AIO12-64MA64 SE, 32 DIF12 44Software500kHz*YesYes21616 I/OYes
DPK-AIO12-64M64 SE, 32 DIF12 44Software250kHz*NoYes21616 I/OYes
DPK-AIO12-64ME64 SE, 32 DIF12 44Software100kHz*NoNo21616 I/OYes
DPK-AI12-64MA64 SE, 32 DIF12 44Software500kHz*YesYes16 I/OYes
DPK-AI12-64M64 SE, 32 DIF12 44Software250kHz*NoYes16 I/OYes
DPK-AI12-64ME64 SE, 32 DIF12 44Software100kHz*NoNo16 I/OYes
RES = resolution   BIP RG = bipolar ranges   Uni RG = unipolar ranges | * = Yes, FIFO
DAQ-PACK with Flexible Signal Conditioning Multifunction Analog Input/Output USB Products
Products # Inputs Res BIP RG Uni RG Gain Speed FIFO AutoCal On-Board # Outputs Res Dig I/O XT
DPK-AIO16-128A128 SE, 128 DIF1699Jumper/Software500kHz*YesYes21616 I/OYes
DPK-AIO16-128E128 SE, 128 DIF1699Jumper/Software250kHz*NoYes21616 I/OYes
DPK-AI16-128A128 SE, 128 DIF1699Jumper/Software500kHz*YesYes16 I/OYes
DPK-AI16-128E128 SE, 128 DIF1699Jumper/Software250kHz*NoYes16 I/OYes
DPK-AIO16-96A96 SE, 96 DIF1699Jumper/Software500kHz*YesYes21616 I/OYes
DPK-AIO16-96E96 SE, 96 DIF1699Jumper/Software250kHz*NoYes21616 I/OYes
DPK-AI16-96A96 SE, 96 DIF1699Jumper/Software500kHz*YesYes16 I/OYes
DPK-AI16-96E96 SE, 96 DIF1699Jumper/Software250kHz*NoYes16 I/OYes
DPK-AIO16-64A64 SE, 64 DIF1699Jumper/Software500kHz*YesYes21616 I/OYes
DPK-AIO16-64E64 SE, 64 DIF1699Jumper/Software250kHz*NoYes21616 I/OYes
DPK-AI16-64A64 SE, 64 DIF1699Jumper/Software500kHz*YesYes16 I/OYes
DPK-AI16-64E64 SE, 64 DIF1699Jumper/Software250kHz*NoYes16 I/OYes
DPK-AIO16-32A32 SE, 32 DIF1699Jumper/Software500kHz*YesYes21616 I/OYes
DPK-AIO16-32E32 SE, 32 DIF1699Jumper/Software250kHz*NoYes21616 I/OYes
DPK-AI16-32A32 SE, 32 DIF1699Jumper/Software500kHz*YesYes16 I/OYes
DPK-AI16-32E32 SE, 32 DIF1699Jumper/Software250kHz*NoYes16 I/OYes
DPK-AIO12-128A128 SE, 128 DIF1299Jumper/Software500kHz*YesYes21616 I/OYes
DPK-AIO12-128128 SE, 128 DIF12 99Jumper/Software250kHz*NoYes21616 I/OYes
DPK-AIO12-128E128 SE, 128 DIF1299Jumper/Software100kHz*NoNo21616 I/OYes
DPK-AI12-128A128 SE, 128 DIF1299Jumper/Software500kHz*YesYes16 I/OYes
DPK-AI12-128128 SE, 128 DIF12 99Jumper/Software250kHz*NoYes16 I/OYes
DPK-AI12-128E128 SE, 128 DIF1299Jumper/Software100kHz*NoNo16 I/OYes
DPK-AIO12-96A96 SE, 96 DIF12 99Jumper/Software500kHz*YesYes21616 I/OYes
DPK-AIO12-9696 SE, 96 DIF12 99Jumper/Software250kHz*NoYes21616 I/OYes
DPK-AIO12-96E96 SE, 96 DIF12 99Jumper/Software100kHz*NoNo21616 I/OYes
DPK-AI12-96A96 SE, 96 DIF12 99Jumper/Software500kHz*YesYes16 I/OYes
DPK-AI12-9696 SE, 96 DIF12 99Jumper/Software250kHz*NoYes16 I/OYes
DPK-AI12-96E96 SE, 96 DIF12 99Jumper/Software100kHz*NoNo16 I/OYes
DPK-AIO12-64A64 SE, 64 DIF12 99Jumper/Software500kHz*YesYes21616 I/OYes
DPK-AIO12-6464 SE, 64 DIF12 99Jumper/Software250kHz*NoYes21616 I/OYes
DPK-AIO12-64E64 SE, 64 DIF12 99Jumper/Software100kHz*NoNo21616 I/OYes
DPK-AI12-64A64 SE, 64 DIF12 99Jumper/Software500kHz*YesYes16 I/OYes
DPK-AI12-6464 SE, 64 DIF12 99Jumper/Software250kHz*NoYes16 I/OYes
DPK-AI12-64E64 SE, 64 DIF12 99Jumper/Software100kHz*NoNo16 I/OYes
DPK-AIO12-32A32 SE, 32 DIF12 99Jumper/Software500kHz*YesYes21616 I/OYes
DPK-AIO12-3232 SE, 32 DIF12 99Jumper/Software250kHz*NoYes21616 I/OYes
DPK-AIO12-32E32 SE, 32 DIF12 99Jumper/Software100kHz*NoNo21616 I/OYes
DPK-AI12-32A32 SE, 32 DIF12 99Jumper/Software500kHz*YesYes16 I/OYes
DPK-AI12-3232 SE, 32 DIF12 99Jumper/Software250kHz*NoYes16 I/OYes
DPK-AI12-32E32 SE, 32 DIF12 99Jumper/Software100kHz*NoNo16 I/OYes
RES = resolution   BIP RG = bipolar ranges   Uni RG = unipolar ranges | * = Yes, FIFO
Acquisition, Control, Communication: Engineering and Systems
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