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## B&k precision dynascan 177 vtvm vacuum tube volt meter

This listing is for a vacuum tube volt meter.
* Make: BK Precision / Dynascan Inspection Systems Corp
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Here is some quick information from the manual...
'I'he greatest of the many advantages ofiered by the VTVM is its high input impedance. This feature makes possible the measurement of voltages in high impedance circuits such as oscillator grid circuits and AGC networks with a much higher degree of accuracy. As a simple illustrative example of this, we have showl in Figure 1A two 500K resistors connected in series across a 100 volt source of voltage. A simple knowledge of basic fundamentals makes it obvious here that the voltagc drop across each resistor will be 50 volts. I\4easuring the voltage across either resistor with a 20K ohm-per-volt non-electronic type instrument on the 0-100 volt scale however, we obtain a reading of only 44 volts. Why the discrepancy. As shown in Figure 1A the meter (on the 100 volt range) can be considered a resistor of 2 meg., which is connected in parallel with the 500K resistor.
A simple Ohm's Larv calculation rvill readily shorv the total resistance of the parallel circuit to be 400K, resulting in a redistribution of the voltage drops in the circuit. Now the first 500K resistor has approximatety 56 volts across it, and the other 500K resistor in parallel with the meter has approximately 44 volts across it. The low resistance meter is loading or changing the impedance of the circuit when it is connected. When a VTVI\{ is used as shown in Figure 18 we have a total of 11 megohms connected in parallel with the 500K resistor, and the total resistance of our parallel network is now approximately 480K, resulting in the voltage across the meter and resistor dropping only to 49 volts or a mere 2/6 lowet than the actual operating voltage. More accurate readings can only be obtained with a high-impedance instument such as the VTVM.
A t/2 volL full scale sensitivity range which permits the accurate reading of the fractions of a volt, (which are often applied between base and emitter of transistor
Anti-parallax mirror permits maximum scale-reading accuracy.
* rnput impedance of 11 megohms on all D.c. voltage rzrnges. This is a very important feature when measuring oscillator grid-bias, AGC/AVC voltage i-i high impedance circuitry.
* special 0-.5 volt D.c. range, useful for accurate measurements of critical circuit parameters in solid state circuitry.
* Measures D.C. voltage up to 1500 volts.
* Measures A.C. RMS voltage up to 1500 volts.
* Measures A.C. peak-to-peak, sine and complex voltages up to 4000 volts.
* Measures resistances up to 1000 megohms.
* Zero center on meter scale, useful for F.M. discriminator aligmment'
* "Transit" switch position automatically clemps and protects meter movement.
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This is used and in good condition. Guaranteed to be in proper working order.
Check out the picture for more information. Feel free to ask any questions. WANT TO REACH ME BY PHONE? Feel free to call me (Trent) toll free @ (***) 972-1346.