25
A better alternative is volumetric sample injection by which the sample is injected into the
flow chamber or nozzle by means of a syringe driven by a motor running at an adjustable,
calibrated speed. An example of such a system is shown in Fig. lOb. Using this method, the
sample flow rate may readily be reduced to 0.1 J.(l/min, and the cell density of the sample can
be calculated directly from the number of cells measured during a given period of time and
the rate of sample injection as given by the motor speed. The disadvantage of volumetric
sample injection is that flushing of the system may be less efficient, although this depends on
the design of the system.
Data systems: The flow cytometer generates a considerable amount of data which the data
system has to handle. For example, five thousand cells/s measured in four parameters, each
of which turns out a 8 bit number, means 20 kbytes/s. Until a few years ago this task required
dedicated computer systems. With the recent advances in computer technology it can now
performed by a PC computer.
The data system of the flow cytometer has four major tasks: 1) To control and record the
various measurement parameters, such as sheath and sample flow rates, electronic amplifier
gains, etc. In the previous generation of instruments, these parameters were set by turning
knobs and recorded by pencil in the lab journal, to the extent that the operator remembered
to jot them down. In most current instruments the measurement parameters are set from the
keyboard of the computer and automatically recorded in its memory. With future instruments
the operator may be able to leave some of the control to the computer, which will supervise
the instrument and automatically optimize the parameters for a given task and level of
performance.
2) A large part of the computer capacity is used to accumulate and store the measuring data .
. The data may be stored either as histograms, or in list mode. In histogram mode, the data are
used to generate histograms, either single parameter histograms or two or more parameters
are combined into multiparameter histograms, whereas the data themselves are not stored. In
list mode, all the measuring data are stored consecutively in the computer memory so that
histograms may be generated by running the data through the histogram generating program
of the system. List mode data acquisition occupies much more computer memory. For
A better alternative is volumetric sample injection by which the sample is injected into the
flow chamber or nozzle by means of a syringe driven by a motor running at an adjustable,
calibrated speed. An example of such a system is shown in Fig. lOb. Using this method, the
sample flow rate may readily be reduced to 0.1 J.(l/min, and the cell density of the sample can
be calculated directly from the number of cells measured during a given period of time and
the rate of sample injection as given by the motor speed. The disadvantage of volumetric
sample injection is that flushing of the system may be less efficient, although this depends on
the design of the system.
Data systems: The flow cytometer generates a considerable amount of data which the data
system has to handle. For example, five thousand cells/s measured in four parameters, each
of which turns out a 8 bit number, means 20 kbytes/s. Until a few years ago this task required
dedicated computer systems. With the recent advances in computer technology it can now
performed by a PC computer.
The data system of the flow cytometer has four major tasks: 1) To control and record the
various measurement parameters, such as sheath and sample flow rates, electronic amplifier
gains, etc. In the previous generation of instruments, these parameters were set by turning
knobs and recorded by pencil in the lab journal, to the extent that the operator remembered
to jot them down. In most current instruments the measurement parameters are set from the
keyboard of the computer and automatically recorded in its memory. With future instruments
the operator may be able to leave some of the control to the computer, which will supervise
the instrument and automatically optimize the parameters for a given task and level of
performance.
2) A large part of the computer capacity is used to accumulate and store the measuring data .
. The data may be stored either as histograms, or in list mode. In histogram mode, the data are
used to generate histograms, either single parameter histograms or two or more parameters
are combined into multiparameter histograms, whereas the data themselves are not stored. In
list mode, all the measuring data are stored consecutively in the computer memory so that
histograms may be generated by running the data through the histogram generating program
of the system. List mode data acquisition occupies much more computer memory. For