Alpha 915 Voltage, Thermocouple, Resistance and Strain Gauge Module
€ - POA
Description
The 915 provides 20 two-pole channels, which can be used for thermocouple, voltage or current measurement. Pairs of these channels can be combined to make four pole measurements for four and three pole resistive, PRT and thermistor sensors. Current energised full bridge strain gauge measurements with four poles are also supported for strain gauge bridges, pressure transducers and load cells. Any odd numbered channel can be paired with the following even channel number to form a four pole channel.
Measurements can be made with up to 19 bit resolution and 1uV integrity.
Thermocouples are cold junction compensated and can be monitored for failure or deterioration during normal operation automatically. Types K,J,T,R,S,E,B and N are supported by the standard firmware.
Current measurements can be made using an external current shunt or with an internal shunt if specified at time of supply.
Resistance, PRT and thermistor measurements can be made with 3 or 4 Terminal sensors with sensitivities of 1mOhm. The PT100 PRT standard and the Fenwall UUB31J1 thermistor are supported in the standard firmware.
Specifications
Specification Details
Number of channels / module 20
Number of 4 pole channels up to 10
Number of 3 pole channels up to 10
Connector type input channels Two part screw terminal.
High quality cage clamp.
Measurement modes T/C
uV DC
mV DC
4-20mA ext shunt
4 Terminal Resistance
3 Terminal Resistance
full bridge strain
A-D CONVERTER:
Five measurement resolutions are supported: 19 bits at 10 measurements
per second
18 bits at 20 measurements/s
17 bits at 40 measurements/s
15 bits at 100 measurements/s
13 bits at 200 measurements/s
In addition a channel filter function can be applied to any channel.
VOLTAGE MEASUREMENT MODE:
Input voltage ranges +10V >-10V
+1.5V >-1.5V
+180mV >-180mV
+23mV >-23mV
Automatic range selection is supported.
DC measurement accuracy +/- 0.015% of reading + 0.01% of range + 6uV
Temperature coefficients DC voltage 25ppm rdg + 0.1uV/oC
Measurement sensitivity <0.25uV on +23mV>-23mV
range at 18 bits
(Note: displayed sensitivity depends on reporting format)
Additional error at 200/sec mode 0.05% of range
THERMOCOUPLE MEASUREMENT ACCURACY:
Internal Cold junction compensation errors included:
(External compensation is also available)
| Type | Range | Accuracy |
| K | -100 to 500 | 0.6 oC |
| 500 to 1200 | 0.7 | |
| 1200 to 1600 | 3.0 | |
| J | -50 to 360 | 0.6 |
| 360 to 800 | 0.7 | |
| T | -150 to 400 | 0.6 |
| R | 0 to 1600 | 2.0 |
| S | 0 to 1700 | 2.2 |
| E | -50 to 290 | 0.7 |
| 290 to 1000 | 1.0 | |
| B | 200 to 1600 | 4.5 |
| N | -200 to 1600 | 1.5 |
| -100 to 580 | 1.1 | |
| 580 to 1300 | 1.3 |
Displayed sensitivity <0.1oC
Thermocouple Health Monitoring Automatic
RESISTANCE MEASUREMENT:
Measurement Ranges
2000 ohm
256 ohm
32 ohm
Sensing Current <0.75 mA (switched)
Accuracy 256R 0.02% rdg + 0.015% rng +2 mohm
4 Terminal mode
RTD MEASUREMENT:
PT100 -50 to 400 oC +/-0.2oC
-150 to 600 oC +/-0.4oC
4 Terminal mode
INTERFERENCE REJECTION:
AC Common mode rejection ratio channel group <0.1uV/V
AC Single channel common mode rejection ratio <1uV/V
DC channel common mode rejection ratio <5uV.V
AC series mode rejection ratio 50 or 60 Hz
+/- 0.05% <1mV/V
Applies to 17,18,19 bit measurements
Maximum voltages operating:
Maximum voltage between any (+) and all (-) inputs 12V
Maximum voltage between any two (-) input terminals 11V
maximum Voltage between any two terminals 22v
OVERLOAD PROTECTION:
Channel overload protection Passive
50V continuous
150V for short periods
ISOLATION:
Isolation test voltage between channel group
and power supply or RS485 Tested at 1000V.
Input current of instrumentation amplifier 5nA
Input impedance of operating >10m 0-12V
POWER REQUIREMENT:
Connector 2 pole screw terminal
Voltage 24V AC l
12 to 28V DC
Current 200mA at 12V
120mA at 24V
