My company, Gentronics, designs a lot of laboratory equipment.
This page lists the most important pieces of equipment I have build.
of these equipment were build on demand for the Medical faculty of the
of Stellenbosch. Other clients also includes the University of the
Cape and the University of Durban Westville. Most of these equipment
are custom made to the client's specifications.
The Gentronics Laboratory rotator has been designed to be used in a
coldroom and is made from aluminum. It also uses an AC synchronous
motor which is controlled by a microcontroller. The microcontrollor not
only regulates the speed, but also protects the motor from overheating
in case the table is unable to move due to obstructions are a too heavy
load on the table.
The Gentronics O2/CO2 gas controller controls the concentration of
oxygen and carbon dioxide. Gas levels are automatically controlled by
either adding air, nitrogen or carbon dioxide to the system. The oxygen and carbon dioxide sensors are both solid state sensors and therefore will have a very long life expectancy if taken good care of. Below is a photo of the unit:
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This electronic timer may be used to switch on any electrical device
for up to 99 hours and 59 minutes. It has a heavy duty relay output and
can switch loads of up to 16A. Below are photos of the electronic timer:
water shut-off valve
This unit is used to automatically shut-off the water supply to a
filtration system if the container is full. The system is started by
pressing the START button, and may be stopped prematurely by pressing
the STOP button. The moment the unit detects that water is flowing out
of the overflow tube from the container, the incoming water supply is
This temperature alarm is used to monitor the temperature of freezers
and refrigerators used in laboratories for storing chemicals and
samples. If the temperature rises above a user settable value, an alarm
output is triggered. I have build two versions of these temperature
alarms. The standard range unit has a temperature range from -40
centigrade to +50 degrees centigrade. The ultra low range has a
temperature range of -100 degrees centigrade to 0 degrees centigrade.
The alarm output is in the form of a normally closed relay, which may
be connected to an alarm circuit. The alarm has a time delay function.
This time delay function is needed since if a freezer is opened to
insert or remove samples, the temperature will rise. Only if the
temperature is above the setpoint for about 60 minutes on the current
units, the relay will open to indicate the alarm condition. During the
time delay the display flashes between the current temperature and the
time which has so far elapsed since the temperature limit has been
This hotplate is used to keep microscope slides at a preset
temperature. The temperature range may be set between 20 degrees
centigrade and 50 degrees centigrade. The hotplate is 300mm by 300mm.
I have recently redesigned the controller electronics of an
incubator prototype which is intended to be used for infants. The
controller currently only controls the air temperature. There are also
built-in alarms for things such as under and over temperature, as well
as battery low conditions. The heater consists of multiple elements,
which switches on according to the temperature difference between the
actual and setpoints.
This device is a 16-channel double pole switch. It uses relays as
The switch position is controlled by a microprocessor. The position is
changed by pressed either the PREV or NEXT buttons. It has two modes,
Normal mode the switch just changes its position in a linear fashion.
Random mode, the new switch position is determined in a random fashion.
High voltage electrophoresis power supplies
These power supplies have a variable voltage output between 0V and
It also has a variable current limit with a maximum current of 100mA.
is a photo of the power supply:
I have also build 300V 400mA versions with seperate voltage and
digital meters. Below is a photo:
Rat heart thermometer
This thermometer uses a small thermistor probe which is used to measure
the temperature of a rat heart on a perfusion system. The temperature
displayed on a LCD display. I have build several of these units. Below
is a photo of one of the
This thermometer has become a vital tool for several perfusion
in South Africa. Temperature plays a very important role in the
of the rat heart, or any other heart, on the perfusion system. In the
several experiments failed because of an error in the temperature.
this thermometer the perfusionist is able to immediate diagnose a
error and make corrections to the water bath's temperature (which is
the same as the heart's temperature).
Below is a more recent version of the thermometers:
ECG Tester Unit
I have build a ECG tester unit to test the anolog input section of ECG
machines. Below is a picture of the ECG tester.
This unit does not generate a true ECG waveform, but it is
to determine if the analog input section of an ECG is working.
The left knob adjusts the heartrate from between 60 bpm and 240 bpm.
The right control is used to put a DC offset between the - and +
Sometimes electrodes acts like batteries, which causes a DC voltage
may overload the input stage of an ECG amplifier. With this control it
is possible to determine what DC level is needed to overload a ECG
The slide switch is used to switch the unit on and off and also to
either 0.1mV or 1mV pulses. The 1mV pulses is the closest to the human
cardiac signal levels. The LED below flashes with each beat. The three
leads of the ECG to be tested is connected to the pins at the bottom.
This temperature probe simulator is used for the calibration of a
thermistor input thermometer (like the rat
heart thermometer or the temperature input of the chart recorder.) It is set up to simulate a
specific thermistor probe. This unit can only be used with
interchangebale thermistor probes, where the tolerances between probes
This simulator is used to test the pressure transducer input of a chart
recorder. It has three sensitivity ranges (2mV/V, 10mV/V and 20mV/V.)
The Benchmark Microplate reader spectrophotometer is connected to a
PC using a standard serial cable. The software runs under Windows 95/98
on the PC. After a reading is taken on the Microplate reader, the
is used to download the absorbance data automaticly from the Microplate
reader to a text file. This text file can then be easily imported into
data processing software.
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