- on Test & Measurement
Apply voltageCheck, before connecting the 12‑V power supply to J1 (+12 V), once more that everything is fitted correctly, and whether the polarity is the right way around. First fit only U3, in order to check the ‑12 V and at the same time check the +5 V and +3.3 V. If everything is okay, the remaining ICs can be fitted in their sockets. After switching on, the contrast will probably have to be adjusted appropriately. There is otherwise a chance that nothing can be seen on the LCD. If the power supply voltage rises to slow, the circuit does not reset properly and only a bar is shown on the display. Therefore always turn the circuit on using the POWER button.
OperationThe operation is straightforward. The setting of the frequency goes quite quickly. When adjusting downwards the cursor automatically jumps back a position. When adjusting up the cursor remains in the corresponding position. The position can be set with the push button on the rotary encoder: when pressed the cursor moves up a position and wraps around, from the highest position the cursor jumps to the lowest position. This has the disadvantage that if you overshoot the desired position when pressing too quickly, you have to press six more times in order to adjust the right position. The lowest frequency that can be set is 1 Hz and the highest is 20 MHz. From 10 MHz to 20 MHz a MSB position is added, but the cursor remains on MHz. Because the amplitude and offset are adjusted using the two potentiometers, they are of course not very accurate. From 10 MHz the amplitude starts to reduce a little and is not stable, probably caused by aliasing. By the way, this instability is already mentioned in the manual. We did not(!?) see a signal on the trigger output (T). The square wave output (SQW) only contains a signal in square wave mode. Take care with these connections, because they are directly connected to the ICs.
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