Model 518 | 8-Channel Smart Sensor Interface
- Measures thermocouples, RTDs, strain gauges, thermistors, voltage and resistance
- 8 high-accuracy differential sensor inputs
- Dynamically reconfigurable, pulsed sensor excitation system
- Supports 4-wire circuits to eliminate lead-loss errors
- Fully electronic calibration
- Low power
Model 518 is an advanced, eight-channel sensor measurement system on a PC/104 board. It generates excitation for passive sensors and provides complete signal conditioning for thermocouples, RTDs, thermistors, and strain and pressure gauges. Each channel can be individually configured to measure voltage, resistance, or any supported sensor type.
The board continuously scans all enabled sensor channels at a 45 channels/second rate. When scanned, each sensor is excited, amplified, digitized, filtered, linearized, converted to engineering units (e.g., °C, Ω, V), and stored in on-board memory, independent of host CPU activity. The host can quickly retrieve the most recent sample from each channel so that it never needs to initiate or wait for data conversion.
Fully electronic calibration is used, thereby preventing calibration loss due to board vibration. Factory calibration data is stored onboard so that model 518 boards can be easily and quickly installed.
Sensoray's exclusive pulsed excitation system provides stimulus for passive sensors. Pulsed excitation reduces sensor self-heating and it also helps to lower the board's overall power consumption.
The excitation system is dynamically reconfigurable; its circuit topology changes as needed to adapt to the type of sensor being measured. For example, a pulsed constant voltage is applied to strain and pressure sensors, whereas pulsed constant current is applied to passive resistive sensors such as RTDs.
Each channel has provision for a four-wire sensor connection that eliminates lead loss errors from RTD, thermistor, and resistor measurements.
Thermocouples are widely used in industrial measurement and control applications because of their relatively low cost and wide temperature ranges. In particular, thermocouples excel at measuring high temperatures where other common sensor types cannot function.
Model 518 includes support for an external cold junction compensation (CJC) sensor, which is required for thermocouple measurements. A CJC sensor is built into several of Sensoray's 518-compatible termination boards. The CJC sensor is measured by a dedicated analog input channel so that the eight sensor channels always remain available for application use.
All field wiring signals are accessible through a 40-pin header. The header may be connected to a custom termination system or to any of several breakout boards available from Sensoray.
Sensoray offers several solutions for connecting model 518 to field wiring. All of the products shown below can be connected to the 518's I/O header with either of two 40-conductor flat cables, models 7409C (18") or 7409C1 (1M).
Model 7409TB is a compact board that breaks out all of the 518's I/O signals to screw terminals. It includes a thermocouple compensation sensor that automatically connects to the 518's CJC input. Thermocouples and other sensors may be directly connected to the 7409TB. For best results with thermocouples, the 7409TB should be insulated from air flows.
Model 7409TDIN is a DIN rail mountable board that breaks out all of the 518's I/O signals to removable screw terminal blocks. It includes a generous prototyping area, and a thermocouple compensation sensor that automatically connects to the 518's CJC input. Thermocouples and other sensors may be directly connected to the 7409TDIN. For best results with thermocouples, the 7409TDIN should be insulated from air flows.
Model 7506TDIN is a DIN rail mountable board that breaks out all of the 518's I/O signals to screw terminals. It does not have a thermocouple compensation sensor, though an external TC compensation sensor may be connected to the appropriate screw terminals if it will be used with thermocouples.
|Input voltage range||Normal operation: ±5 V
Absolute max: 63 VAC rms, applied for up to 2 seconds
|A/D converter||16-bit integrating|
|Conversion time||22 mS per channel|
|A/D scan rate||45 samples/second|
|Input impedance||1000 MΩ|
|CMRR||95 db, min|
|Power and Environmental|
|Input power||+5 V @ 100 mA
-12 V @ 35 mA
+12 V @ 45 mA
|Operating temperature||-25 to 85°C|
|Thermocouple||J, K, T, S, E, B, N, C, R|
|RTD||Platinum: 100 ohms, types 385 and 392
Nickel: 120 Ω, 200 Ω, 1000 Ω
Copper: 10 ohms
|Thermistor||10 KΩ, YSI type 44006 or 44031|
|Strain gage||120 to 4000 Ω|
|Model 518 Technical Manual||1.0.0||280 KB|
|Model 518 tech support wiki|
FAQs, examples and additional information
|Model 518 Mechanical Drawing||1.0.0||22 KB|
|Smart A/D Software Development Kit|
Latest for Windows 7
|Smart A/D Software Development Kit|
Legacy for Win2000 & XP
|Other Operating Systems|
|Need a software development kit for another operating system? We can port our SDK to|
your OS or provide the information you need to do it yourself. Contact Sales for details.