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.
|Published (Last):||2 June 2005|
|PDF File Size:||12.8 Mb|
|ePub File Size:||14.8 Mb|
|Price:||Free* [*Free Regsitration Required]|
Transistor Q2 is a grounded emitter power amplifier which is used to vary the collector voltage of Q1. For a typical RF diode detector of the type used in RF millivoltmeters, a square law response or transfer function is obtained for signals below approximately 30 millivolts mVa linear response or transfer function is obtained above approximately mV, and the response between approximately 30 and mV is in transition between square law and linear.
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. The voltmeter matches the characteristics of the probe by processing the signal on leadwhich is representative of the probe output, in a square root converter circuit and a linear amplifier having inputs in parallel, and then mixing their outputs in various proportions as is appropriate for each voltage range by use of the precision resistance network I just picked up two of these cheap.
I forgot my password. 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. The machine has a good frequency response, small standing wave co-efficient, high sensitivity, low power consumption, small size and is light weight. In the Ballantine Model A RF millivoltmeter, which is constructed generally in accordance with the embodiment described here, the following semiconductor device types have been used: Is the probe proprietory or can I make a probe?
The square root converter U6 provides the proper linearization and calibration for the 1 mV through 30 mV Ranges.
High rms accuracy, traceable to NIST, is assured regardless of waveshape. 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 of the diode detector, and means for displaying the amplitude value of the resistance network output signal.
Still, it may be possible to obtain a schematic and parts list, and maybe come up with a home-built version that would work okay at lower frequencies. The output DC voltage at leads and is a function of the amplitude of the input signal on lead The precision resistor network comprising resistors R52, RR63, plus the feedback network of meter amplifier U9, performs the required scale linearization.
The apparatus of claim 5 wherein the diode detector is a germanium point contact diode. 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.
The good thing with this meeter is that the probe is attached. Range switching in this embodiment of my invention is accomplished electronically by use of field effect transistor FET switches. 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.
Aug Thu 25, You won’t be able to get the engineering and parts required for the bandwidth. Buffer amplifier circuitalso shown in FIG. Ballantine A RF millivoltmeter Posted: As a result of this filter, the response is down 3 dB at 2 Hz and falls at a rate of 10 dB per octave. Resistor R72 adjusts full scale calibration of the indicating meter. Aug Thu 25, 3: The output of the detector is filtered by a filter formed by resistors R1-R4 and capacitors C2-C5.
RF voltmeters without probes are truly a dime a dozen.
3440A RF Millivoltmeter | Ballantine
The probes are usually much more complicated than that. I have seen pallets of these meters at surplus sales, all wrapped in plastic, without a single probe ,illivoltmeter the bunch. And its detachable design reduces your work in servicing. Table 1 above includes a truth table for FET switch U8.
The instrument is 3440z in rms of a sine wave. TLC’s which are connected in an instrumentation amplifier configuration with very high common mode rejection.
Ballantine RF Millivoltmeter 3440A With Accessory Kit
That detected signal is then applied in parallel to the inputs of both a square root response channel and a linear response channel which millivoltmster include an amplifier. 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.
My Boonton’s use special diodes in the probe for full-wave rectification, which is then converted back to AC in the instrument via a mechanical chopper. Aug Tue 23, 2: Common calibration errors are eliminated through temperature compensation of the probe detector diodes; double shielding protects the interchangeable probes from rough handling and pickup.
The voltmeter of claim 1 millivooltmeter comprising an adjustable gain input amplifier connected to receive the diode detector output and ballanine to provide the diode detector signal to the square root converter and to the linear amplifier.
Tact-switches are used for longer duration. In the embodiments of FIGS.
Broadband voltmeter – Ballantine Laboratories, Inc.
The detector operates in the square law region below 30 mV rms input and the instrument provides millivolt,eter response in this region. In the 3 mV range, the reference is reduced by a voltage divider comprising resistors R82, R83, R84 and R86, to correspond to the reduction in gain of the preamplifier The resistor network R e determines the proportions of Vs and V a as components of V 4.
Showing results 1 – 9 of 9 products found. If you can find a diagram for the probe, you might be able to make something up using low-barrier diodes, but you’d have to verify the calibration and you would probably lose performance at the higher frequencies.
By amplifying the signal before detection, the entire detector output can be placed in the linear response region and no further compensation is required.
A SumoBrain Solutions Company. Annoying to say the least I’m sure there are other good solutions out there as well.
Thanks for all the information, these definitely were gov’t, there is a USMC callibration on one of them. These characteristics cause the probe to have high input impedance over the very wide frequency range from 10 kHz to beyond 1.