Several AM25Ts can connect
to one datalogger
Overview
The AM25T 25-Channel Solid State Multiplexer increases the number of thermocouples that can be measured by a Campbell Scientific datalogger. The multiplexer interfaces with the datalogger and adds terminals for wiring additional thermocouples or other low-level voltage output sensors.
Read MoreBenefits and Features
- Greatly increases the number of thermocouples a data logger can measure
- Multiplexes up to 25 thermocouples
- Includes an on-board PRT that serves as a reference junction
- Allows several AM25Ts to be controlled by one data logger, increasing the number of thermocouples that can be measured
- Uses a metallic, internal ground plane to reduce thermal gradients, which ensures more accurate measurements
- Provides a vertical package for a smaller “footprint” that makes it easier to fit in a crowded enclosure
- Supports a maximum cable length of 152.4 m (500 ft) when lightning protection is used
Images
3D/CAD Files:
Detailed Description
Up to 25 thermocouples are sequentially connected to a common differential channel on the AM25T. The output from this channel is wired to a differential input channel on the datalogger. As the AM25T sequentially changes channels, the datalogger measures the output from each thermocouple in sequence.
A PRT attached to the AM25T’s grounding bar provides a temperature reference for the thermocouple measurements. The heat capacity of the grounding bar and an insulated aluminum cover reduce thermal gradients along the length of the multiplexer. Reducing the thermal gradients allow more accurate measurements.
Specifications
| Expandability |
|
| Internal PRT Accuracy |
|
| Power | 9.6 to 16 Vdc (under load), unregulated |
| Typical Relay Resistance | 500 Ω |
| Maximum Switching Current | 25 mA (Switching currents greater than 25 mA will damage the relays and render them unusable.) |
| CE Compliance | Conforms to EN55022-1:1995 and EN50082-1:1992. |
| Operating Temperature Range | -40° to +85°C |
| Operating Humidity Range | 0 to 95% (non-condensing) |
| Dimensions | 23.6 x 5.1 x 13.2 cm (9.3 x 2 x 5.2 in.) |
| Weight | 0.9 kg (2.0 lb) |
Typical Current Drain |
|
| Quiescent | 0.5 mA |
| Active | 1.0 mA |
Enable Levels |
|
| Inactive | < 0.9 V |
| Active | 3.5 to 5 V |
Clock |
|
| Levels | Scan advance occurs on the falling edge of the clock pulse (from above 3.5 V to below 1.5 V) |
| Minimum ON Time | 50 µs |
| Minimum OFF Time | 60 μs |
Compatibility
Please note: The following shows notable compatibility information. It is not a comprehensive list of all compatible products.
Dataloggers
| Product | Compatible | Note |
|---|---|---|
| 21X (retired) | ||
| CR10 (retired) | ||
| CR1000 (retired) | ||
| CR1000X | ||
| CR10X (retired) | ||
| CR200X (retired) | ||
| CR206X (retired) | ||
| CR211X (retired) | ||
| CR216X (retired) | ||
| CR23X (retired) | ||
| CR295X (retired) | ||
| CR300 | ||
| CR3000 (retired) | ||
| CR310 | ||
| CR350 | ||
| CR500 (retired) | ||
| CR5000 (retired) | ||
| CR510 (retired) | ||
| CR6 | ||
| CR800 (retired) | ||
| CR850 (retired) | ||
| CR9000X (retired) |
Mounting Equipment
| Product | Compatible | Note |
|---|---|---|
| ENC10/12 | ||
| ENC10/12R | ||
| ENC12/14 | ||
| ENC14/16 | ||
| ENC16/18 | ||
| ENC24/30 | ||
| ENC24/30S |
Additional Compatibility Information
Sensors
The AM25T is typically used with type T, E, J, or K thermocouples; different thermocouple types are also supported (depends on data logger model and operating system). The AM25T can also measure other sensors that have a low-level voltage output. However, the AM25T should NOT be used with resistive bridges or be configured with a voltage divider between the AM25T and the data logger. The AM16/32B multiplexer is available for these applications.
Software/Programming
The AM25T is controlled by the AM25T instruction in CRBasic. When using Edlog, data logger Instruction 134 is used with recently shipped versions of the data loggers; older data loggers can measure and control the AM25T with a series of data logger instructions.
Short Cut software (available free of charge from our website) supports simple programming and generates wiring diagrams for AM25T applications; older versions of Short Cut did not support multiplexers.
Enclosure Considerations
The AM25T operates in most field conditions but requires a non-condensing environment. Outdoor applications require a weather-resistant enclosure augmented by desiccant; a Campbell Scientific enclosure is recommended.
Our ENC12/14 enclosure can house up to two AM25Ts, a CR800, CR850, CR10X, CR1000, or CR3000, and a power supply. The ENC16/18 houses several AM25Ts, a CR800, CR850, CR10X, CR1000, CR3000, or CR5000, and a power supply.
Documents
Product Brochures
Frequently Asked Questions
Number of FAQs related to AM25T: 3
Expand AllCollapse All
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Bridge-type circuits (107/108 probes, PRTs, load cells, strain gages, and pressure transducers) should be used with the AM16/32(A or B) to preserve measurement accuracy and repeatability. Voltage signals (thermocouples, thermopiles, and high-level voltages) can be used with the AM25T multiplexer without any degradation to measurement accuracy or repeatability.
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The AM25T was designed specifically to interface to Campbell Scientific data loggers only, with no provisions to interface to third-party devices.
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The AM25T is typically used with thermocouples. It uses solid-state relays, which have a varying impedance from one closure to the next. This impedance is higher than the impedance in the mechanical relays used in the AM16/32-series multiplexer or the retired AM416 multiplexer. Bridge circuits (107/108 probes, PRTs, load cells, strain gages, and pressure transducers) should not be connected to the AM25T because of the varying and higher impedance values (compared to the AM16/32).
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