Technical data
A/D converter	8 bits, 80 MHz sampling frequency
Data buffer	256 or 512 bytes (software selected), about 21000 bytes for periodic signal
input amplifier	gain: x1 or x2 (software selected), bandwidth 25MHz
input voltage	AC, max. 1V p-p
input impedance	50 Ohm or 1M Ohm (jumper)
post-trigger (t_pom)	0 - 255µs (software selected)
external trigger	max. 2kHz

The card generates the following control signals:
· T_NAD pulse generator control signal;
· STEP step motor control signal;

and has the following input signals:
· EXT_TRG external trigger;
· ZERO position marker signal (e.g. generated by an optical sensor).

	Block diagram of the card
	gain Uin w_trg EXT_TRG TTL reset T_NAD TTL status STEP TTL t_pom ERO TTL pomiar	gain control input signal trigger select external trigger card reset pulse generator control measurement status step motor control measurement time control position marker measurement start

One of the most important features of the card is a precise synchronization between the transmitter trigger signal T_NAD and the moment when the sampling of the input signal starts.

This time (t_pom) is software programmable in the range of 0 - 255µs with a resolution of 1µs and has stability within the range of 1ns. It is particularly important in the case of scanning devices, since it allows to achieve a very small time skew between different positions (channels). 1ns would correspond to a clock frequency of 1GHz which is much higher than the actual frequency used.

Automatic measurement mode

The card in its standard version can operate with a moving measurement head (rotating or moving linearly) as well as with a multiplexer circuit switching measurement channels. It can control a step motor (through a driver unit).

· ZERO is a marker of the reference position of the measurement head;
· STEP is a signal controlling the step motor driver unit or the multiplexer;
· T_NAD triggers the transmitter circuit, it is synchronized with the STEP signal in such a way that
· a pulse on the STEP signal is followed by a delayed pulse on the T_NAD signal as shown in a figure below.
· The delay is introduced in order to eliminate potential interference from the step motor.

Oscilloscope mode

In this mode, for each EXT_TRG pulse, a single T_NAD pulse is generated (the STEP signal is not generated). This permits a precise synchronization with the clock signal generated on the card and therefore guarantees good repeatability of measurement results. In the case when the measurement circuit cannot be triggered, the repeatability of measurement results corresponds only to the clock resolution (12ns).

In the current version of the card, there is no analogue trigger input and this function is implemented in software.

The card is programmed through the I/O operations. The STATUS and ZERO signals can be checked by reading the status register. The STATUS signal can also generate an interrupt.

Thanks to the feature which allows the I/O base address change, a number of our cards can work in a single computer.

All the control signals generated by the card can be modified according to specific customer requirements. For instance, a number of T_NAD pulses can be generated between consecutive STEP pulses, the frequency of the STEP pulses can be modified etc.

Included with the card is software which operates in both the automatic and oscilloscope mode. It also has a spectrum analysis function.

Future versions of the card will include:

1. 16-bit data bus and a programmable sampling frequency;
2. Data buffer located in the memory address area of a PC;
3. Large data buffer which will enable a fully autonomous measurement cycle;
4. Increased sampling frequency to at least 200 MHz;
5. PCI interface.