ohms per volt การใช้

• The sensitivity of an analog multimeter is given in units of ohms per volt.
• The meter movement itself is 20, 000 ohms per volt and 50 microamperes full scale.
• An improved version of 1927 increased this to 13-ranges and 166.6 ohms per volt ( 6 mA ) movement.
• After 1945 / 6, 20, 000 ohms per volt became the expected standard for electronics but some maker offered even more sensitive instruments.
• For example, a very low cost multimeter with a sensitivity of 1000 ohms per volt would draw 1 milliampere from a circuit at full scale deflection.
• Between the mid 1930s until the 1950s, 1000 ohms per volt became a de facto standard of sensitivity for radio work and this figure was often quoted on service sheets.
• The sensitivity of such a meter can be expressed as " ohms per volt ", the number of ohms resistance in the meter circuit divided by the full scale measured value.
• A " Universal " version having additional alternating current and alternating voltage ranges was offered from 1933 and in 1936 the dual sensitivity Avometer Model 7 offered 500 / 100 ohms per volt.
• The technical specifications of these devices were often crude, for example the one illustrated has a resistance of just 33 ohms per volt, a non-linear scale and no zero adjustment.
• A power factor and wattage unit was also available ) . 500 ohms / volt with divide by two button in normal position, 1000 ohms per volt with divide by two button pressed.
• However, some manufacturers such as Simpson, Triplett and Weston, all in the USA, produced 20, 000 ohm per volt VOMs before the Second World War and some of these were exported.
• The movement drew 12mA for full-scale deflection and used a " universal shunt " permanently in parallel with the movement which increased the input terminal full-scale current to 16.6mA, corresponding to 60 ohms per volt.
• Its maximum current draw of 50 ?A at full-scale deflection ( corresponding to 20, 000 ohms per volt ) is sufficient in most cases to reduce voltage measurement error due to circuit loading by the meter to an acceptable level.
• For example, a meter with a sensitivity of 1000 ohms per volt would draw 1 milliampere at full scale voltage; if the full scale was 200 volts, the resistance at the instrument's terminals would be ohms and at full scale the meter would draw 1 milliampere from the circuit under test.
• The first Avometer had a sensitivity of 60 ohms per volt, three direct current ranges ( 12 mA, 1.2 A, and 12 A ), three direct voltage ranges ( 12, 120, and 600 V or optionally 1200 V ), and a 10, 000 ohm resistance range.
• More expensive, ( and mechanically more delicate ) multimeters typically have sensitivities of 20, 000 ohms per volt and sometimes higher, with 50, 000 ohms per volt ( drawing 20 microamperes at full scale ) being about the upper limit for a portable, general purpose, non-amplified analog multimeter.
• More expensive, ( and mechanically more delicate ) multimeters typically have sensitivities of 20, 000 ohms per volt and sometimes higher, with 50, 000 ohms per volt ( drawing 20 microamperes at full scale ) being about the upper limit for a portable, general purpose, non-amplified analog multimeter.