USB compatible 8-channel sensor interface | Model 2218
- Measures thermocouples, RTDs, strain gauges, thermistors, voltage and resistance
- Provides complete sensor signal conditioning
- High-accuracy differential inputs
- Excellent 50/60 Hz rejection
- Pulsed excitation minimizes sensor self-heating
- 4-wire circuits eliminate lead-loss errors
- Isothermal connectors for high thermocouple accuracy
- Powered by USB
Model 2218 is a USB-compatible module that interfaces eight sensors to a host computer. It provides excitation for passive sensors and complete signal conditioning for thermocouples, RTDs, thermistors, and strain and pressure gauges. Each channel can be independently configured to measure voltage, resistance, or any supported sensor type. In addition, eight independent digital I/O lines (3.3 V logic) are available for general-purpose use. All GPIOs support edge detection, programmable direction and software-configurable pull-up/pull-down control. The module is USB-powered; no external power supply is required.
The module automatically scans the eight sensor channels and produces up to five samples/second per channel. When scanned, a sensor is excited, cold-junction compensated, amplified, digitized, and linearized as required by the sensor type. Samples are automatically converted to appropriate engineering units (e.g., °C, Ω, and V) and sent over USB at a programmable rate so that the host computer never needs to initiate or wait for data conversion.
Sensoray's exclusive pulsed excitation system provides the ideal stimulus for passive sensors. Excitation is applied only when measuring, thus reducing both sensor self-heating and overall module power consumption. The excitation type and level is automatically reconfigured, on-the-fly, for each channel to optimize sensor stimulation.
Each channel has provision for a four-wire connection, enabling it to completely eliminate lead loss errors from RTD, thermistor, and resistor measurements.
The module eliminates several common sources of thermocouple measurement error. Its novel internal design eliminates module-induced thermal gradients, and a removable cover is provided to insulate thermocouple cold junctions from disruptive thermal transients.
Fully electronic calibration is used to ensure rock-solid performance in high-vibration environments. Factory-programmed calibration data is stored in the module to enable quick and easy installation.
Robust, removable screw terminal blocks are provided for all field wire connections. Analog signals connect to a cluster of four terminal blocks along one side of the module; digital signals connect to a single terminal block on the opposite side.
|Number of channels||8|
|Interface||4-wire (2 excitation, 2 analog input)|
|Input voltage range||Normal operation: ±5 V
Absolute max: ±20 V
|Scan rate (per channel)||Up to 5 samples/s|
|Input impedance||1000 MΩ|
|CMRR||78 db @ 0-60 Hz, min|
|Thermocouple||J, K, T, S, E, B, N, C, R|
|RTD||Pt 100 α = 385
Pt 100 α = 392
Ni 200 α = 1.098
Ni 1000 α = 4.4
Cu 10 α = 0.039
|Thermistor||10 KΩ types 44006 / 44031|
|Strain gage||120 Ω min|
|Voltage ranges||±5 V
|Resistance ranges||0 to 400 Ω
0 to 4 KΩ
0 to 600 KΩ
|Number of I/Os||8|
|Interface||3.3 V CMOS logic|
|Programmable functions||Edge detection, direction, pull-up/down configuration|
|Interface||USB 2.0 high-speed|
|Input power||USB powered, 1.75 W (350 mA @ 5 VDC)|
|Operating temperature||0 to 70 °C|
|Storage temperature||-25 to 85 °C|
|Model 2218 mechanical drawing||1.0.0||64 KB|