AM16/32B (16- or 32-Channel Relay Multiplexer)
The AM16/32B multiplexer significantly increases the number of sensors that you can measure with a Campbell Scientific data logger. It interfaces with the data logger and adds terminals so that you can wire additional sensors of almost any type.
Benefits and Features
- Significantly increases the number of sensors the data logger can measure
- Can multiplex 16, 32, or 48 sensors
- Supports many types of sensors including thermistors, potentiometers, strain gages, vibrating wires, reflectometers, and soil moisture blocks
- Decreases the cost of cabling individual sensors on long wire runs
- Allows a relay address to be used to go directly to a specific channel—reducing power consumption and wear on the relay switches
- Electrical surge protection via gas tubes on all analog I/O, and varistors or TVS diodes on all other connections
- Prevents sensor-cable damage by providing strain relief for sensor leads and independent routing for sensor shield lines
- Eliminates the requirement for dc blocking capacitors for gypsum soil moisture blocks, significantly reducing sensor cost
Depending on sensor type, the AM16/32B can multiplex 16, 32, or 48 sensors. Up to six AM16/32Bs may be connected to the same data logger, depending on the number of control ports and analog inputs available.
The AM16/32B either multiplexes 16 groups of four lines (a total of 64 lines) through four common (COM) terminals. Alternatively, a manual switch setting allows the AM16/32B to multiplex 32 groups of two lines (also a total of 64 lines) through two COM terminals. A cable connects the common terminals to data logger analog inputs, excitation channels, or ground as required by the sensor. The data logger controls the multiplexer using two control ports, or one control port and one excitation channel.
Electrical Surge Protection
The equipment is protected from electrical surges using gas tubes on all inputs. A 35 V varistor is connected between the shield ground and ground lug to provide surge protection. The Reset, Clock, and +12 V terminals are protected by 18 V TVS diodes.
|-NOTE-||The protection on the reset, clock, and +12 V inputs are provided by 18 V TVS diodes.|
|Power||Unregulated 9.6 to 16 Vdc|
|Scan Advance||Occurs on the leading edge of the clock pulse transition (from below 1.5 V to above 3.3 V)|
|Minimum Clock Pulse Width||1 ms|
|Maximum Actuation Time for Relay||20 ms|
|Relay Operation||Break before make|
|Initial Relay Resistance, Closed||0.1 ohm|
|Maximum Switching Current||500 mA
(Switching currents greater than 30 mA [occasional 50 mA current is acceptable] will degrade the contact surfaces of the mechanical relays and increase their resistance.This will adversely affect the suitability of these relays to multiplex low voltage signals.Although a relay used in this manner no longer qualifies for low voltage measurement, it continues to be useful for switching currents in excess of 30 mA.)
|Maximum Switching Voltage||50 Vdc
A voltage divider such as the VDIV10:1 may be needed between the AM16/32B and the data logger to stay within the input limits of the data logger channel.
|Minimum Contact Life||5 x 107 operations|
|Maximum Contact Voltage Rating||70 V|
|Maximum Voltage||8 Vdc (clock level)|
|Surge||Complies with IEC61000-4-5, test level 3 (±2 kV, 2 ohm coupling impedance)|
|Operating Temperature Range||
|Dimensions||23.9 x 10.2 x 4.6 cm (9.4 x 4.0 x 1.8 in.)|
|Weight||~680 g (~1.5 lb)|
|Air Discharge||Complies with IEC61000-4-2, test level 4 (±15 kV).|
|Contact Discharge||Complies with IEC61000-4-2, test level 4 (±8 kV).|
Typical Current Drain
|Quiescent||< 210 µA|
|Inactive||< 0.9 V|
|Active||3.3 to 8 V|
Note: The following shows notable compatibility information. It is not a comprehensive list of all compatible or incompatible products.
|CR300||CRBasic programming experience is recommended, as the AM16/32B with the CR300 series is not currently supported in Short Cut.|
|CR310||CRBasic programming experience is recommended, as the AM16/32B with the CR300 series is not currently supported in Short Cut.|
|CR350||CRBasic programming experience is recommended, as the AM16/32B with the CR350 series is not currently supported in Short Cut.|
|ENC10/12||Mounted sideways only.|
Additional Compatibility Information
Data Logger Considerations
A series of data logger instructions control the AM16/32B operation (measurement instructions that are repetitive are generally contained within a programming loop; in the CR800-series, CR1000, CR3000, and CR5000, this functionality is available in the SubScan instruction).
Compatible sensors include thermistors, potentiometers, load cells, strain gages, vibrating-wire or vibrating-strip transducers, water content reflectometers, and soil moisture blocks. The AM25T is recommended for multiplexing thermocouples.
Maximum Number of Sensor Connections
The maximum number of sensors multiplexed through one AM16/32B depends on the type(s) of sensors measured. For example, assuming identical sensors, the AM16/32B can multiplex up to:
- 32 single-ended or differential sensors that require two wires (for example, thermistors, half bridges)
- 16 single-ended or differential sensors that require four wires (for example, full bridges, four-wire half bridges)
- 32 vibrating-wire sensors (16 with temperature) in conjunction with an AVW1, AVW4, AVW100, or AVW200-series Vibrating-Wire Interface
- 48 half-bridge measurements (assumes common excitation and completion resistors at the data logger)
- 48 CS616 Water Content Reflectometers (assumes common excitation)
- 32 gypsum soil moisture blocks (model 223 or 253). The AM16/32B eliminates the requirement for dc blocking capacitors, significantly reducing sensor cost
The AM16/32B draws less than 210 microamps quiescent, 6 milliamps active—so power considerations are heavily tied to the percentage of time in quiescent versus active states. Use of a relay address can reduce power consumption by minimizing the time spent in an active state.
In most applications, the data logger’s sealed rechargeable power supply should be more than sufficient; the data logger’s alkaline power supply could be used in applications where the multiplexer is activated infrequently.
The AM16/32B operates in most field conditions but requires a non-condensing environment. A weather-resistant enclosure equipped with desiccant is required for field use. A smaller enclosure is often used if the multiplexer is housed at a distance from the data logger.
If the AM16/32B is to be housed in the data logger’s enclosure, one AM16/32B, a CR800, CR850, CR1000, CR3000, or CR10X datalogger, and a PS150 power supply will fit in an ENC12/14. For convenience in wiring, a larger enclosure (e.g., ENC16/18) is recommended.
LoggerNet, PC400, and ShortCut are compatible with the AM16/32B. Short Cut software (available at no charge from our website) supports simple programming and generates wiring diagrams for AM16/32B applications; early versions of Short Cut did not support multiplexers. Please reference the notes in the compatibility table for data loggers.
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