It’s the “no probes” part that’s the killer here. The probes are what gives the meter its bandwidth. Probes are usually bad because users like to measure the signal. Schematic of Boonton Model 92 A RF Millivoltmeter; Boonton Electronics Corp. . In the Ballantine Model A RF millivoltmeter, which is. The old Boonton RF Millivoltmeter or Boonton RF Microwattmeter or . Ballantine Labs A Standard RF Probe – 10KHz to GHz with pf.
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Numerous calibration adjustments are required with such successive approximation type millivoltmeters in order to optimize the match to the detector response.
ff Auto measuring range switching makes your usage more convenient. The signal at the output of amplifier A 3 is applied to a square root converter SR and to a linear operational amplifier A 4.
A RF Millivoltmeter | Ballantine – TechRecovery, LLC
The square root converter U6 provides the proper linearization and calibration for the 1 mV through 30 mV Ranges. While the effect of the approximation steps may not be noticeable in such an instrument using an analog type meter, they would be noticeable when a digital meter with 0. The other thing is that I seem to recall that the probes are serial number matched to the instrument. The Ballantine A still appears to be a current instrument, and a rather nice one.
Calibrator for calibration and testing of A.
Only goes down to mV, though. The good thing with this meeter is that the probe is attached. First, everything has to be well sheilded, since even an exposed probe tip can pick up enough RF “noise” to throw off your readings.
This detection usually takes place in a meter probe. Showing results 1 – 9 of 9 products found. The gain of amplifier U4 is set by the ratio of the fixed resistor R37 connected between terminals 10 and 13 and the resistance coupled between terminals 14 and 2 which is varied by the operation of a three-pole double throw switch U5 typically a RCA type No. My invention is also useful for narrower bandwidth devices where it is desireable to provide a transition between square law and linear function ranges, including meter circuits employing diode detectors preceded by an amplifier.
Manufacturers Ballentine Laboratories, Inc.
Ballantine RF Millivoltmeter 3440A With Accessory Kit
Your suppose to be able to use it with any digital or analogue multimeter. The outputs of the square root response channel and the linear response channel are then combined by a precision resistor network to obtain the optimum match abllantine the diode detector for each 10 dB meter range without any approximation steps within each such a range.
Resistors R10 and R81 in the buffer amplifier circuit are used for meter zero adjustment. They exhibit extremely high back resistance and have very low junction capacity.
As a result of this filter, the response is down 3 dB at 2 Hz and falls at a rate of 10 dB 3440w octave.
Ballantine RF Millivoltmeter A With Accessory Kit | eBay
Aug Tue 23, In the 10 mV range, a further reduction is provided by substituting resistors R85 and R87 for resistors R84 and R86 in the voltage divider. Users browsing this forum: Preamplification at first appears to be the ideal solution. This instrument has a 4 digit display with high precision, small frequency effected errors and high input impedance. The instrument is calibrated in rms of a sine wave. Click on a button to share this product: Aug Fri 26, An additional four transistors are similarly arranged to approximate the required response in the mV range, three more are used for the mV range, two more millivlltmeter the 1 V range, and one for the 3 V range.
This switching arrangement balances the various internal leakage currents in the FET switches of U3 at pin 2 of each of amplifiers U1 and U2, providing a common mode signal. It’s a foam lined plastic box with the probe and various adapter tips. Can you roll your own? Not that I’ve had much luck with this myself, but you could also try calling Ballantine tech support and asking if they ballntine any “B” stock or used probes, or perhaps nallantine that won’t meet spec, that they could let go for cheap.
An eight-position range control switch S2, shown in FIG. Range switching in this embodiment of my invention is accomplished electronically by use mi,livoltmeter field effect transistor FET switches. Since this transition region is often an important region for voltage measurement, as are ballanhine regions above and below, it is necessary to avoid or compensate for the transition response characteristic as well as to provide the appropriate response in the square law and linear regions.
Where I am convinced that they were supplied to people who didn’t have the slightest clue how to use them. Transistor Q2 is a grounded emitter power amplifier which is used to vary the collector voltage of Q1.
In the Ballantine Model A RF millivoltmeter, which is constructed generally in accordance with the embodiment described millivolgmeter, the following semiconductor device types have been used: You won’t be able to get the engineering and parts required for millivoltmeeter bandwidth.
There was a QEX magazine article a while back about building a compensated RF voltmeter using a pair of matched diodes and some high-impedance opamps, if you want to homebrew something. Two principal techniques have been employed to deal with the low level and transition region response characteristics: The general nature of my invention is best explained in connection with FIG. Measuring RF at microvolt levels presents a whole bunch of challenges.
Gain is set at approximately -1 resistors R64 and R66 in conjunction with the resistor network More like hundreds of millivolts at best. Still, it may be possible to obtain a schematic and parts list, and maybe come millivoltemter with a home-built version that would work okay at lower frequencies.
A voltmeter comprising a diode detector, a square root converter and a linear amplifier each connected to receive the diode detector output signal, a resistance network connected to receive the outputs of the square root converter and the linear amplifier, means for selectively switching the resistances of the resistance network to change the proportion at the resistance network output between the signal from the square root converter and the signal from the linear amplifier to inversely match the response curve millivolltmeter the diode detector, and means for displaying the amplitude value of the resistance network output signal.