DESCRIPTION

Running experiments in parallel rather than in series greatly increases throughput and makes better use of time and equipment. The RM-8 respirometer multiplexer allows you to select from any one of seven respirometer sample streams with full baselining available at any time on the eighth channel.

Each stream consists of a pair of precision, fast-operating electrical valves.  When activated, these valves connect the selected stream to a pair of common ports.  The RM-8 can switch between streams and baselines manually or automatically, between or during recordings with appropriate software, such as ExpeData. Manual channel selection, or user-programmed channel selection (up to 99 steps), or daisy-chainable serial (RS-232) channel selection can also be selected.  In digital mode (TTL-level control signals) two multiplexers can be used together for a total of 16 sample streams. For more than 16 sample streams, use serial (RS-232) mode to connect up to 8 RM-8 units.

What happens to respirometer chambers that are not selected?  

The RM-8 allows respirometer chambers that are not selected to be flushed continuously with a user-provided airstream to prevent hypercapnic or hypoxic conditions from developing between readings. Alternatively, the FlowBar-8 mass flow generator can be used to control air-flow independently through all chambers at once, and the RM-8 can then be used to sub-sample the air emerging from each chamber, allowing very fast switching from chamber to chamber. The optional stop-flow configuration prevents any gas flow while the chamber is not selected, supporting intermittent flow respirometry applications.

Optional Configurations 

• RM-8-1: Unit is delivered configured for stop-flow respirometry with the solenoids sealed and the flush circuit disabled.
• RM-8-2: Subsampling ‘half-multipelxer’. This unit has only a single row of eight solenoids with no purge circuit.  It is intended to support applications where a continuous flow through multiple chambers is needed.
• RM-8-3: The standard RM-8 design but with a smaller internal volume to minimize dead space and lag when flow rates < 100ml/minute are used. The RM-8-3 is delivered configured for open flow.  For low flow rate stop-flow respirometry, order one of our stop-flow conversion kits ( KIT-RM-8-1

Optional Electrical Multiplexer Accessory: MUXSCAN

By using this adapter, you can quickly and easily connect up to 8 activity detectors or other transducers (range: 0 to 5V) to your RM-8, and the adapter will select the appropriate detector automatically when its corresponding multiplexer channel is selected. The MUXSCAN  also has provision for biasing resistive detectors such as thermistors, light dependent resistors (handy for activity detection at moderate light levels) and phototransistors using either visible light or invisible infrared illumination.

 

The RM-8 can be configured for flow-through or stop-flow respirometry as demonstrated in the following graphs. 

Example of Flow-through Multiplexing on n=4 laboratory mice (flow rates=2 LPM). Baselines are conducted every 2.5 minutes. Note that a dwell time of only 30 seconds is sufficient to determine metabolic rates.

 

Example of Stop-flow Multiplexing on n=8 chambers each containing n=10 Drosophila (Flow rates=100ml/min). Baselines are conducted every 10 minutes. Note that the integral of each peak is directly proportional to metabolic rates.

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