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Emco V-20 Operating Manual
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Emco V-20 Operating Manual

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Summary of Contents for Emco V-20

  • Page 3: General Description

    The quality of this instrument is further exemplified by the inclusion of wire-wound potentiometers (shunting and in series with the rectifier), which are factory adjusted to compensate for the individual characteristics of the rectifier in your instrument. This built-in EMCO feature assures you of standardized accuracy over a wide range of measurements.
  • Page 4 Decibels -12 to -55 db in 5 ranges (calibrated for use across a 500 ohm line Resistance Range Center Scale 0 to 2000 ohms (12 ohms) 0 to 0.2 meg (1200 ohms) 0 to 20 megs (120,000 ohms) Overall Dimensions 6-3/4"...
  • Page 5 power when connecting or disconnecting the test leads. The meter and the leads must not be handled while the power is e. DC voltages are read on the black 0-10, 0-50, 0-250 scales marked D.C. When using the 10, 50, and 250 volt ranges, the meter may be read directly.
  • Page 6 which the current to be measured is flowing (observing current direction). If you have mistaken the direction of current flow, the pointer will be deflected left of zero, in which case simply reverse the test leads. d. Currents in either the 10 ma range or the 10 amp. range are measured with the RANGE switch in the 10MA- 10AMP.
  • Page 7 a. Find the point corresponding to the frequency of the applied voltage on the horizontal scale marked "cycles per second.” b. Trace upwards from that point until you strike the curve corresponding to the range on which you are measuring. c.
  • Page 8 An external AC power source is required to make capacitance and inductance measurements. 1. Set up the MODEL V-20 and the external power source as shown in figure 2. WARNING: Make certain the external power source is off before connecting the capacitance or inductance to be measured.
  • Page 11 High Resistance Measurements NOTE: An external DC power source variable up to 250V; a 270K, 5% resistor; and a 180K, 10% resistor are required to make high resistance measurements. Set up the Model 565 (555) and the external components and power supply as shown in figure 3.
  • Page 12 WARNING: Make certain the external power source is off before connecting the resistance to be measured 2. Set the DC-AC-OUTPUT switch to the DC position and the RANGE switch to the 250V position. 3. Adjust the DC power source for a full-scale reading of 250 volts with the meter leads connected across resistor Rl.

  • Page 13: Circuit Theory

    CIRCUIT THEORY Introduction The purpose of this section is to describe the theory of operation of each of the measuring circuits available with this instrument. Simplified individual schematic diagrams accompany each of the circuit descriptions. DC Voltage Measurement Figure 4 shows that portion of the 565/555 meter circuit used for DC voltage measurements. Contacts 7-10 of OUTPUT-AC-DC function switch S2 are closed in this mode.
  • Page 14 AC Voltage Measurement Figure 5 shows that portion of the V-20 meter used for AC and output voltage measurements. Contacts 8-10 and 2-4 of function switch S2 are closed for AC measurements. Here again, jacks J3 and J4 are used to measure all AC voltages except 5KV, in which case J3 and J6 (A.C.
  • Page 15 must be placed in series with meter MI so that the meter will provide the proper reading for the selected range scale. The following contacts of S1E represent the five available voltage ranges: 8 - 1KV/5KV; 9 - 250V; 10 - 50V; 11 - 10V; 12 - 2,5V.
  • Page 16 AC series resistors are 1/20 the value of the DC resistors. Resistance Measurement Figure 6 shows that portion of the V-20 meter circuit used for resistance measurements. With the unit used as an ohmmeter, function switch S2 is in the DC-OHMS position and contacts 7-10 are closed. Resistance measurements are made between jacks J3 and J4.
  • Page 17 of the selected ranges. Potentiometer R28 is used to compensate for variations in the battery voltages, thus allowing the meter to be zeroed for each range. DC Current Measurement Figure 7 shows that portion of the V- 20 meter circuit used for DC current measurements. In this mode, function switch S2 is in the DC-OHMS position;...

  • Page 18: Maintenance

    Decibel Measurement The operation of the DB range (see figure 5) is essentially the same as that described under Output Voltage Measurement. The meter is calibrated in DB across a 500 ohm impedance. MAINTENANCE General This instrument should require very little, if any, maintenance due to its inherent ruggedness and ability to withstand electrical surges.
  • Page 19 MODEL V-20 Please add the following to your OPERATING MANUAL. On page 2, after the title OPERATING INSTRUCTIONS, insert the following paragraph: Before proceeding, remove the instrument from the cabinet. Insert a large flashlight battery. D-Cell, into the battery bracket mounted on the wall of the bakelite case The Positive terminal of the battery is to face up towards the top of the case.
  • Page 20 Schematic...
  • Page 21 Component Location 1...
  • Page 22 Component Location 2...
  • Page 23 Parts List...
  • Page 24 Page Left Blank Intentionally...

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