Chromatography trace for protein purification FRACTION COLLECTORS


RDn can interface with virtually any model of a fraction collector. Typically, the detector 'listens' for a fraction change signal from the fraction collector, displays the actual number of the fraction as a numbered tick mark on the screen, and stores the fraction count in the output file.

During the purchase, a customer may inform REACH Devices about the brand of the fraction collector he/she intends to be using with RDn. In this case, a connection cord with a connector fitting this particular fraction collector will be provided. If needed in the future, this cord can be cut and outfitted with a different connector to fit another fraction collector’s brand.

If a collector connection cord was ordered, but no fraction collector type was specified in the Purchase Order, a generic cord will be provided. The Generic Cord can be adapted to be used with essentially any fraction collector. The adaptation is straightforward and described in the detector's manual. The adaptation requires the fraction collector's manual and basic soldering skills.

The detector has an HR-25A 8-pin female socket (Hirose Electric Co Ltd, mating connector part number is HR25A-7P-8P), which provides the possibility to communicate with various external hardware.

Pins 1-4 simultaneously supply up to four galvanically isolated analog output signals in 0 to 1V range, that are always active while the Acquisition Screen is displayed. Output transfer functions can be set by user in “Settings” menu. (An output transfer function specifies what output voltage corresponds to a particular signal value). Note that Pin1 may be reconfigured in the “Settings” menu to output any channel including pH.

Pins 5 and 6 provide digital outputs that can be programmed by REACH Devices upon customer's request. Pin 7 provides an input that has a 5K pull-up resistor to +5V. Open collector, open drain, TTL/CMOS (active low) or mechanical switch are all acceptable sources to be attached to Pin7. During data acquisition, a transition from logical 1 to 0 level (aka contact closure) is recorded to data memory as an external fraction number. This is implemented for faction collectors that produce an electrical pulse when they change the fraction. Note that only one transition per acquisition rate would be recorded. So, if the detector acquisition rate is set to 1 second (default), then fraction collector should not output more than 1 pulse per second.

In general, depending on the collector's brand, two types of interface are possible:

1. Event Marker / Tube change: output on the faction collector, input on the detector. The detector 'listens' for a fraction change signal from the fraction collector, displays the actual number of the fraction on the X axis, and stores the fraction count in the output file. In this scenario, typically, the fraction collector fraction change event output should be connected to Pin7 of the detector with a shielded cable.

2. Analog output: input on the faction collector, output on the detector. The detector supplies the fraction collector with an analog signal proportional to a channel output (UV250, UV280, Conductivity or RI) chosen by the user. The collector is programmed by the user to perform the tube change depending on the value of the data signal. In this scenario, typically, Pin1 of the detector should be attached to the analog input of the fraction collector. It is very important to use a shielded cable.

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