Alpha 915 Voltage, Thermocouple, Resistance and Strain Gauge Module

€ - POA



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.


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
4-20mA ext shunt
4 Terminal Resistance
3 Terminal Resistance
full bridge strain


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.


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


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


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


PT100  -50 to 400 oC                              +/-0.2oC

-150 to 600 oC                                         +/-0.4oC

4 Terminal mode


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



Channel overload protection                                     Passive

50V continuous

150V for short periods


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



Connector                                                                   2 pole screw terminal

Voltage                                                                        24V AC l

12 to 28V DC

Current                                                                        200mA at 12V

120mA at 24V



915 Brochure: [Download]

MN915 Issue1: [Download]

Alpha Programming Manual: [Download]