Voltmeter, digital

The voltage output of the more common types of thermocouple is of the order of 50V/C and the output is either read on a sensitive moving-coil meter or on a digital voltmeter. The reading is converted to temperature using a calibration chart supplied with the thermocouple. Some commercial units are available in which the thermocouple and instrument is supplied as an integral unit with the scale directly calibrated in temperature. If a separate instrument is to be used then it should be noted that the thermocouple resistance is only of the order of 10 and... 

However, in the case of stress-corrosion cracking of mild steel in some solutions, the potential band within which cracking occurs can be very narrow and an accurately known reference potential is required. A reference half cell of the calomel or mercury/mercurous sulphate type is therefore used with a liquid/liquid junction to separate the half-cell support electrolyte from the process fluid. The connections from the plant equipment and reference electrode are made to an impedance converter which ensures that only tiny currents flow in the circuit, thus causing the minimum polarisation of the reference electrode. The signal is then amplifled and displayed on a digital voltmeter or recorder. 

The simple electrical circuit shown in Fig. 16.15(h) is suitable for this procedure. The voltage applied to the titration cell is supplied by two 1.5 V dry cells and is controlled by the potential divider R (a 50-100 ohm variable resistance) it can be measured on the digital voltmeter V. The current flowing is read on the micro-ammeter M. 

Nonlinear and discontinuous equations can be easily implemented, e.g., to simulate the effects of a temperature-limiting device or a digital voltmeter. ... 

Digital voltmeter or digital multimeter, like the one used in Experiment 15... 

Next, notice the outlined vertical box on the right side of the amplifier module board. This experiment involves two items in this box. The first is the voltmeter connection (labeled DVM for digital voltmeter) with switch (SW3). When the switch is down, the DVM measures the voltage at socket P45. When the switch is up, the DVM measures the voltage at socket P44. The second item with which this experiment is concerned is the signal/power connector, a category 5 connector. It is at this connector where the battery module will be connected. 

The electrical circuit, Figure 17.2 (b), consists of two 1.5 V dry cells that provides a voltage applied to the above titration cell. It is duly controlled and monitored by the potential divider (R) and is conveniently measured with the help of a digital voltmeter (V). Finally, the current flowing through the circuit may be read out on the micro-ammeter (M) installed. 

Digital noise measurements have been obtained by use of a microcomputer controlling the sampling rate of a sensitive digital voltmeter employed to measure the potential or current fluctuations. The subsequent analysis of the derived time records is described. 

A Hewlett Packard HP85 Microcon juter A Hewlett Packard 3478A Digital Voltmeter A "custom built" multiplexer... 

The sait5)ling rate of the digital voltmeter (DVM) was controlled by the microprocessor and channel selection for monitoring was obtained by utilising a pulse output from the DVM. 

A typical measuring circuit is shown in Fig. 9.15. A signal generator supplies a sinusoidal signal with 600 fl output impedance. The current is amplified at sensitivity of 10 AfV. The ac voltages are measured by ac digital voltmeters. The experiment is performed with a PZT-4 tube, provided by EBL, Inc., with L = 25.4 mm, D = 12.7 mm, h = 0.50 mm, and Y= 7.5 X 10 N/m. The lowest resonance frequency is 5 kHz. The results of measurements are shown in Fig. 9.16. The current, about 1 xA, can easily be measured with 1% accuracy. The current from the two x quadrants agrees well with that from the two y quadrants. In terms of the units mentioned, the piezoelectric coefficient dn can be obtained from directly measurable quantities as ... 

Figure 8.2 The digital ohmmeter uses a constant-current source to produce a voltage across the unknown resistance proportional to its resistance, and a digital voltmeter to read that voltage.

Potential noise is measured by collecting the potential versus time record between a noisy corroding electrode and a noiseless reference electrode using a high-impedance digital voltmeter (DVM). This is essentially a measurement of... 

Prior to applying a potential of -1.0 V, the open circuit potential will be monitored. Verify with the second measuring RE (connected to the WE through a digital voltmeter) that the open circuit potential is approximately the same no matter where the measuring RE is placed with respect to the WE surface. Cell connections, shown in Fig. 30 are as follows ... 

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