Some physical experiments (e.g. mass spectrometry) have a need to count the number of pulses per time frame. The device which was developed at our institute is furthermore capable of communicating with stepper-motors, a temperature regulator, a voltage measuring board and a quadrupole.
All these features are combined in a single device:
A Matlab program (running under LINUX) commands the TOF device via a standard RS232 interface. The modules inside the device are talking on a 2nd RS232 line.
BAL_TOF1: This slave module can be considered as the core of the whole device, as it provides the time framed counting of the incoming pulses. Some Verilog code was implemented on a FPGA, in order to provide the following features:
With this handheld, battery powered device the user can easily measure voltages in the range of ±2 V and log the data to a compact flash card.
The resolution is 14Bit (1 LSB equals to 250µV). The sampling frequency is selectable and can be up to 1 MHz.
The incoming pulses are counted and displayed as
counts / stotal counts
The data can also be acquired via a RS-232 port - either in the auto-output mode or in the polling mode.
A pushbutton or a command from the serial port resets the counter.
Each channel can provide up to 1000 W heating power! The desired temperature can be set from 50 °C to 200 °C. The actual temperature is measured by a standard type K thermocouple.
230 V (european) outlets are used to connect the high-voltage heating elements.
The regulation is controlled by a microprocessor. The power section is opto-isolated from the controll-stage.
Most photodiodes have a current output. In order to make this generated signal more handy special amplifier circuits (transimpedance amplifiers) are needed.To avoid ringing, to achieve a good signal to noise ratio and to get the desired signal amplitude the amplifier must be matched with the photodiode used. Therefore no run of the mill amplifier can be used or must at least be modified.
Many photodiode amplifiers have already been developed at our institute. Some have a high gain, others also control the peltier cooling of the diode.
When you look for a quick way to test 2-wire slave ICs your search has come to an end.
Simply use a standard RS-232 terminal program, send ASCII commands to this device and you have got a 2-wire Master!
This portable device can be powered by either 4 AA battery cells, or by an external power supply.
The voltage for the 2-wire interface can be 3.3 V or 5 V and the baudrate of the RS-232 is also selectable.
The logic level of 2 BNC connectors can be programmed in order to generate test pulses. Furthermore you can insert time delays, which may also be helpful when exploring a new chip.
Programmable pull-up resistors and clock speed complete the functionality of this handheld unit.
Manual and technical documentation
Some experiments call for accurate time measuring.
Say you want to calcute the earth's acceleration by measuring the time of a free falling body and you are showing the experiment in an ample lecture hall. Then you need a counter with big digits.
The all-purpose counter developed by M. Hafner at our institute has the following features:
Have you ever been in the enervating situation that you had to connect a device via its RS-232 interface, but you could not match the interface parameters?
Here we present a device which overcomes this pain:
The RS232 parameters of each side can individually be set. A buffer ensures that bytes, received at a higher baudrate than sent out, are not lost.
The main aim of a scan generator is to provide a accuratee, linear sweep voltage. In most cases a triangular or sawtooth wave form is used. The generated voltage ramp can then control other device, such as laser control boxes or deflection systems.
Are you already using FTDI's FT245R chip to establish a simple connection between your microcontroller (or CPLD, FPGA) target board and your personal computer?Then you will also desire a terminal program for your PC, which works similiar to Hyperterminal or other RS-232 terminal programs:
FT245R_Term is a first try to bridge the gap.
The project was done in C# (.NET application) under the SharpDevelop Enviroment.
Institut for Experimental Physics Graz University of Technology Petersgasse 16/1.KG A-8010 Graz Austria Tel.: +43 (0) 316 / 873 - 8148 Fax: +43 (0) 316 / 873 - 8655 j.friedrichnoSpam@tugraz.at
Monday - Friday 08.00 - 16.00
All images © TU Graz/Institute of Experimental Physics