Features
- 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
- Transparent cold-junction compensation for thermocouples
Model 518 is a smart 8-channel sensor measurement system on a PC/104 board. 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.
The board automatically scans all enabled sensor channels at an aggregate rate of 45 samples/second, yielding a per-channel rate of approximately 5.6 sps when all channels are active. When scanned, a sensor is excited, amplified, digitized, linearized, converted to appropriate engineering units (e.g., °C, Ω, V), and stored in on-board memory. The host can quickly retrieve the most recent sample from each channel so that it never needs to initiate or wait for data conversion.
Excitation
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 board power consumption.
Lossless measurement
Each channel has provision for a four-wire connection, enabling it to completely eliminate lead loss errors from RTD, thermistor, and resistor measurements.
Thermocouples
The board automatically performs cold junction compensation in conjunction with an optional, external temperature transducer. A dedicated input is provided for the transducer so that all eight sensor channels are preserved for application use. A compatible transducer is integrated into several SENSORAY termination boards; click the Accessories tab above for details.
Calibration
Fully electronic calibration is used to ensure rock-solid performance in high-vibration environments. Factory-programmed calibration data is stored on-board to enable quick and easy installation.
Sensor Connections
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.
Specifications
| Sensor channels |
|---|
| Number of channels |
8 |
| Interface |
4-wire (2 excitation, 2 analog input) |
| Input voltage range |
Normal operation: ±5 V
Absolute max: ±20 V |
| A/D converter |
Integrating, variable resolution |
| Aggregate scan rate |
45 samples/s |
| Per-channel scan rate |
5.6 samples/s |
| Input impedance |
1000 MΩ |
| CMRR |
78 db @ 0-60 Hz, min |
| CMV range |
±5V |
| Power and environmental |
|---|
| Input power |
Rev V+ (currently in production): +5 V @ 300 mA
Rev A-U (legacy): +5 V @ 100 mA, -12 V @ 35 mA, +12 V @ 45 mA |
| Temperature |
Operating: 0 to 70 °C
Storage: -25 to 85 °C |
| Supported sensors |
|---|
| 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
±500 mV
±100 mV |
| Resistance ranges |
0 to 400 Ω
0 to 4 KΩ
0 to 600 KΩ |
Accessories
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.
7409TB — compact breakout board with TC compensation sensor
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.
7409TC — DIN rail mountable breakout board with TC compensation sensor and prototyping area
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.
7506TDIN — DIN rail mountable breakout board