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DataTaker

CEM20 Expansion Module

The CEM20 (Channel Expansion Module) is DataTaker’s proprietary relay multiplexer designed to scale up sensor capacity cost-effectively without requiring multiple master loggers.

  • How it Connects: A single CEM20 connects to just one of the master logger’s 4-wire universal analog channels for data transmission, alongside standard 12V power and digital control lines. The modules can be daisy-chained up to 100 meters away from the host logger.
  • Channel Multiplication: Each module adds 20 universal, fully isolated differential channels. Because it inherits DataTaker’s dual-channel isolation technology, each of those 20 channels can be split. A single CEM20 can handle:
    • 20 fully isolated 3-wire or 4-wire inputs (like RTDs or strain gauges).
    • Up to 40 isolated 2-wire inputs.
    • Up to 60 common-reference 2-wire inputs (like single-ended voltages or thermocouples).
  • System Limits: * The mid-range DT80 supports up to 5 CEM20 modules, scaling it to 100 differential channels (up to 300 single-ended inputs).
    • The advanced DT85 supports up to 16 CEM20 modules, turning a single logger into a massive data acquisition node with 320 differential channels (up to 960 single-ended inputs).
  • Efficiency: The CEM20 features ultra-low power consumption. It is automatically powered down by the master logger’s switched 12V output when a sampling schedule is idle, preserving battery life in remote deployments.

High-Density Scaling of DT8x Data Loggers

Diagram above shows functional connections for DT80 data logger and two CEM20 units. Cable lengths should always be kept as short as possible to minimise noise and signal losses.

Each CEM20 can add 20 analogue input channels for sensors supported by DT80 range loggers, includes thermocouples, Vibrating Wire Strain Gauges, RTDs, 4-20mA loops, voltage,
resistance, frequency etc.

  • The mid-range DT80 can  connect any of its 5 terminal blocks to a CEM20 module. Allowing it to be scaled up to 100 differential channels or 300 single-ended inputs.
  • The advanced DT85 connect any of its 16 terminal blocks to a CEM20 module. Allowing it to be scaled up to 320 differential channels or 960 single-ended inputs.

CEM20 modules only support the DT80 and DT85, series 2 and above. To expand the DT82I, use a Modbus network with the DT82I as the Modbus Master, a capability shared by all three models.

You can view the compatible loggers on the pages linked below.

https://www.omniinstruments.co.uk/our-brands/datataker/industrial-loggers/

https://www.omniinstruments.co.uk/our-brands/datataker/geotechnical-loggers/

Applications

Expanding sensor counts for manufacturing lines where high-density temperature, pressure, or flow monitoring is required.
Enabling large-scale multi-point monitoring of environmental sensors in remote or complex field deployments.
When paired with custom subsea enclosures, the CEM-20 allows for deep-sea instrumentation and monitoring on the UK Continental Shelf at depths reaching 4,000m.
Scaling bridge or building sensor networks by adding high-density differential inputs for strain gauges and bridge sensors.

Frequently Asked Questions

▶ Q: Which data loggers are compatible with the CEM-20 expansion module?
A: The CEM-20 is specifically designed for use with the DataTaker DT80 and DT85 range of data loggers (including DT80, DT80G, DT85, and DT85G series). Please note that it requires Series 2, Series 3, or Series 4 loggers; it is not compatible with the older Series 1 models.
▶ Q: How many sensors can I connect to a single CEM-20 module?
A: Each CEM-20 adds 20 universal analogue channels. Depending on how your sensors are wired, a single module can accommodate: Up to 20 fully differential (4-wire) sensors (e.g., RTDs/PT100s, full-bridge strain gauges); Up to 40 3-wire sensors; Up to 60 single-ended (2-wire) sensors (e.g., thermocouples, 4-20mA current loops, or voltage inputs sharing a common return).
▶ Q: How many CEM-20 modules can I daisy-chain to a single data logger?
A: You can connect multiple modules to scale up your system significantly. A DT80 logger can support up to 5 CEM-20 modules (expanding the system up to 100 differential or 300 single-ended inputs), whilst a DT85 logger can support up to 16 CEM-20 modules (expanding the system up to 320 differential or 960 single-ended inputs).
▶ Q: Does the CEM-20 use up any channels on the master data logger?
A: Yes. Each CEM-20 module connects to one analogue block on the host DT80 or DT85 data logger. The master logger uses this channel to multiplex through the 20 channels on the expansion module.
▶ Q: What types of sensors can I connect to the CEM-20?
A: Because it features universal inputs, you can mix and match a wide variety of sensors across the module, including: Thermocouples (Types B, C, D, E, J, K, N, R, S, T); RTDs (PT100, PT500, PT1000); Thermistors; Resistance (up to 10k ohms); Bridge sensors (Strain gauges, load cells); Voltage (up to ±30V); Current (4-20mA loops, using an external precision bypass resistor)
▶ Q: Can the CEM-20 be used in harsh or outdoor environments?
A: The standard CEM-20 comes in an enclosure meant for clean or industrial control cabinet installations. However, Omni Instruments can supply the CEM-20 pre-configured in a variety of custom protective enclosures, ranging from portable weatherproof cases for field research, wall-mounted enclosures for fixed locations, or even specialised subsea pressure housings rated for depths up to 4,000 meters.
CEM-20

CEM-20

The CEM20 is the Channel Expansion Module for DT80 and DT85 data loggers Series 2 and above. This allows a further 60 single ended inputs (voltage, current or Thermocouple) or 20 fully differential inputs (PT100 or bridge) to be added to the DT80 or DT85. One full analogue input channel on the logger is used to connect the CEM 20.

£1,100.00
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