Filter
Top Products
15
7. VOLTAGE LEVEL MEASUREMENTS USING THE SELECTIVE MODE
7.1 General - The HP3586 can only output level measurements in db’s referenced to a power like one
miliwatt, one picowatt, or a voltage level like .775 volt on all models and a 1 volt input on the C version.
But remember that every level reading is only in db referenced to a power or voltage level. If you’re not
familiar with this comparative nonlinear system of measurement, take a look at Appendix A for a better
understanding. Now let’s do a couple of examples of voltage measurements.
A very important consideration is that if we were going to do a voltage measurement of a very high
impedance tuned circuit where the instrument’s unterminated 10K 50pf input would load or detune, we
need to insert a one to one probe or amplifier to isolate the HP-3586’s input. In Appendix C I’ve shown
the schematics of two circuits you may want to consider to isolate the circuit under test from you
instrument.
7.1 Performing the Measurement - First let’s use the first example of the padded output oscillator in
the previous example. This is very easy to do by first recalling our configuration stored in the 1 location
by pressing [RECALL], entering 1 on the keyboard. We first need to change the measurement units for
voltage measurements, press [db.775V] on the measurement/entry sub panel. If the offset button’s light is
on, press this button to deactivate the offset calculation. Now our readings of the oscillator’s output will be
in units of db referenced to .775 volts. We can easily calculate the level in volts using a calculator and the
following formula:
Level in volts = 20 anti log (Vr /. 775) Where Vr is the display panel reading in db.775V units.