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Voltamper characteristic of the bulb

Apparatus – measuring principle

As with the Voltamper LED characteristic, the task measurement principle is based on the standard V-A characteristic of the general electronic element. Using the variable source, we change the voltage on the measured element (here the bulb) and on the ammeter that is connected in the circuit we read the size of the respective electric current. The V-A characteristic in this task is measured point-by-point, ie the gradual measurement of voltage-current pairs in the set range of values. The circuit diagram is shown in Figure 1.

schema zapojeni V-A charakteristiky zarovky
Fig. 1   Schematic diagram of the experiment for measuring the V-A characteristic of the bulb

pohled na ulohu

In the case of our remote VeLMA experiment, we draw on the same scheme, only the regulated source and the measuring instruments replace the K8055 measuring card. One of the two digital-analogue outputs is current-enhanced and serves as a regulated source with a maximum voltage of approx. 5 V. Analog-digital inputs serve as a pair of voltmeters. One measures the voltage on the measured bulb, the other measures the voltage on the resistor. From the knowledge of the voltage on the linear element (resistor), Ohm's law can determine the current passing through the resistor and hence the bulb - see the diagram (Figure 1). The effect of the current flowing (eg the moment when the light bulb is lit, the intensity of its light… etc.) can be observed using the connected webcam.

Both measured experimental values (i.e., U and I) are read and displayed on the control panel in a client-side web browser. Such measured values can be stored in a table (file) and displayed on a chart continuously. Continuous display of values in a graph directly on the task measurement panel serves primarily for orienta- tion checking the accuracy of the measured data or for finding the locations of the characteristics where the necessary data needs to be assembled. For complete processing according to the assigned task, the data can be stored on your PC and processed there in any spreadsheet calculator - MS Excel, OO Calc etc.

VELMA - zpracování dat v Excelu

Because the device is very similar to the NICoL (Voltamper LED characteristic), it has been jointly implemented on the same K8055 USB card. Tasks, however, are now solved so that they can be independently controlled, despite the use of a single control card for both tasks. Independent management of two tasks with a single K8055 card is currently (according to available information) unique worldwide!

Video tutorial