The B and B were made with ten biscuit type layer cells. Modern equivalents are constructed from round button cells hence the R in the type number. The meter battery contacts seem to have been changed in the late 's from the flat type shown here to pointed spring contacts more suitable for the BLR types. BLR Height: 36mm. Width: 15mm. Length: 26 mm. BLR Height: 34mm.
Diam: 15mm. These can still be obtained but prove to be very expensive. I have successfully refilled the plastic casing with ten new cells obtained from a "Pound Shop". Insert 1. Note that this cover unlike the one for the Model 7 has an additional slot for a spring loaded hook probe which is often missing. This one is the same as the model 8 Mk1 except that it is fitted with an extended metal push button with rubber boot to reverse the moving coil.
This type of pushbutton was used on some miitary versions but not all and some if not all have a steel outer casing with an earthing terminal. These instruments preceded the Test Set No. With the change to the familiar red and black terminals new leads and prods were made and the battery cover was a simple piece of metal with two keyholes and a piece of expanded rubber to keep the 1.
Click to download Instruction booklet. Click to download backplate instructions the Mk1 and Mk2 had the same instructions. II from advert This instrument has been produced in response to a demand for a high sensitivity version of the world-famous Model 7 AvoMeter. It follows the standard design, retaining the traditional simplicity of operation and compact portability.
It has a sensitivity of 20, ohms per volt on all D. In addition to the many well-known features such as the automatic overload protection device, dual-knob range selection, etc. Shrouded plug in type leads are now supplied with all AvoMeters. This is the inside of a model 8 Mk2 showing the four inner leaf springs which make connections between the battery compartment and the meter movement and the two outer ones which make connections to the HV terminals.
A panclimatic version of the model 8 was introduced in the early s. Electrically and mechanically the same as the model 8 it was a tropicalised version incorporating encapsulated components and using materials resistant to mould growth. Under bright light as can be seen on the image here the moulding material for the casing and knobs has a brownish tinge. Later versions were given the title Test Set No.
The model 9 was intended for the export market and is similar to the Model 8 MarkII apart from the international symbols and ranges instead of 2. No dB scale; resistance on bottom of scale plate instead of top; no LR or Ins. Click here for Instruction manual. The rear of the front panel of a Model 8 MkII the switching arrangement for models 7,8 and 40 etc is much the same.
Battery compartment found on Model 8 Mk2 and 9 Mk2 instruments. The Bakelite cover was changed to a simple metal part with keyholes on the Mk2 and Mk3 instruments see below. Note that Test set No1 was made for several years and was based upon the current commercial model at the time. Test set No. At some point added fuse on low ohms ranges.
This model is housed in a protective steel case. No dB scale; resistance on bottom of scale plate instead of top, no LR or Ins. DC 3, 10, 30, , , , , volts - sensitivity 50 uA DC 0. Later versions of 'Test Set No. Battery Compartment. You can see that one fuse is a spare and unconnected.
The negative contact of mine is a bit green and you will see that I have split open the case of the original battery to refill with new button cells. Replaced copper-oxide with germanium rectifiers to improve AC sensitivity and frequency response typically 20K Hz at 2. These were not incorporated in Model 9 until the Mark 4 version.
Fuse added to low ohms ranges. Early models of the Mk3 do not incorporate the additional protection features described below and shown on the circuit diagram. Looking at the diagram on the right the meter has thermal compensation plus additional protection diodes around the movement and in circuit with the ohms range. The ohms range was vulnerable to putting it across AC so the diodes back to back would protect the meter and draw the current through the fuse.
Previous models it seems would not be protected if on the DC setting but were connected to a high AC supply voltage. Note the changes to the battery contacts and the shaped rubber spacer to keep the 1. Previous models often only had red blobs of paint to indicate how the batteries should be inserted. This is a later and more sensitive version of the Braille model7 shown above. Have a look here for a description and additional pictures of this model:.
New internal construction using PC boards. Wired connections to battery compartments. Reliability problems with this model no military versions. AC sensitivity increased again. Housed in plastic case. Mirror placed mid scale rather than at bottom as on all previous versions. This was the last model to have leather rather than plastic carrying strap. The Avometer Model 8 Mk 4 incorporates all the traditional design features of its predecessors, so highly valued for Simplicity, together with such additional features as: increased sensitivity in the lower a.
It also incorporates the familiar Avo automatic cut-out mechanism and a decibel scale for audio frequency tests. DC 50uA to 10A f. Resistance: 0 to 20M ohm First indication 0. Size: x x mm.
Weight: 2. This is the first model to have wired connection between the battery compartment and the meter. The spare fuse is housed in a hole on the right. Access by removing the back cover. This meter was equipped with an electronic voltage converter which was supplied from the 1. This item is normally supplied with a flexible printed connector though in my case the previous owner had soldered wires to the 1.
See here for more information. This one in my collection has no date. It is designed primarily for the electronics engineer and is similar in specification to the Avometer Model 8 Mk.
The Model 9 incorporates all the traditional design features of the Model 8 including the Avo automatic cut-out mechanism and reverse moving coil facility. The Model 9 is, however, scaled in basic units of 10 and 3 and all range switches, controls and terminals are identified by graphical symbols, which in general follow the requirements of the International Electrotechnical Commission.
The protective devices incorporated in the Model 8 Mk. The decibel scale is, however, not included on this instrument. C, 50uA to 10A f. Resistance: 0 to 20M a first indication 0.
Sensitivity: A. The case and battery compartment on the later model 8Mk4 and model 9Mk4 are shown here. Similar to the design adopted for the subsequent models. Test Set No1 Mk3 is the military version of this instrument.
New internal and external design including movement, the new plastic front-panel no longer includes the word "Universal" Plastic casing redesigned. Leather carrying handle abandoned for a plastic one. Instrument much lighter than all previous models. But LR could still be measured with Resistance Range unit. Adopted Model 9 ranges and added volts AC range. It is essentially the same apart from front panel markings and a different instruction plate on the back.
A military version ' Test Set No. Production of the iconic model 8 meter ceased in Though known for their Avometer general purpose multimeters, they made a wide range of test gear including valve testers, oscillators and light meters. You will find more information here about these instruments and other similar models. AVO also produced a range of smaller multimeters which are described here. AVO Model 8 sometimes referred to as the 8 Mark 1 this original model with replacement movement. I also have another made in given to me by Ian Griffiths.
The model 9 MkIV is electrically the same but has International standard markings on the front panel and scale. All these models have As can be seen the front panel, range selection switches and meter scale markings are substantially the same.
The instruction plates on the rear of the instruments are different, the later instruments indicate that they were manufactured by AVO Ltd, Dover, England and that AVO was a member of the Thorn Group for a period. There are other significant differences: 1 The original model has black terminals of the same type as the Model 7 and model 40 instruments and does not have a Volt DC range. AVO multimeters are renowned for their reliability and robustness, the incorporation of a mechanically operated cut out linked to the meter movement and the two switch range selection system have endeared these meters to generations of electrical and electronic engineers.
AVO Model 8 interior [The penciled number on the meter magnet reads and that on the back of the scale plate is ]. Not much changed on the inside over the years. Note how the MkIII instrument has been opened and repaired over the years from to When this instrument was given to me by Charles Husband the glass had become detached from the casing, the pointer was slightly bent and the batteries of vintage had leaked and corroded the battery terminals, these were easy enough to rectify and the meter worked on all ranges apart from the resistance ones.
I eventually found that there were two problems: The contacts for the fuse were also corroded and the high resistance prevented the instrument from being zeroed.
The contacts which were meant to be closed on the resistance ranges were dirty and causing erratic readings. It looks as if the meter has been repaired as the serial number on the scale has been obliterated, the genuine AVO leads are replacements and the instruction manual is that for a MkIII meter.
It arrived in this purpose made cardboard box which has kept it in first class condition.. What is it worth? Read the comments at the bottom of the page before considering the purchase of one of the later models. Instructions on rear panel These are often very difficult to read so here you will find Model 8 Mk II - Rear panel text.
How old is it? Most AVO meters can be dated from the last 3 or 4 digits of the serial number under the right hand end of the scale. The serial number on later models have a self adhesive sticker on the right hand side of the case. These define the month and year of manufacture. Please download avometer manual and circuit diagram.
Page 1 of 1. Add Comment. Notify me of new comments via email. I have read and agree to the terms and conditions. By submitting a comment, you are declaring that you agree with these rules: Although the administrator will attempt to moderate comments, it is impossible for every comment to have been moderated at any given time.
You acknowledge that all comments express the views and opinions of the original author and not those of the administrator. You agree not to post any material which is knowingly false, obscene, hateful, threatening, harassing or invasive of a person's privacy. The administrator has the right to edit, move or remove any comment for any reason and without notice.
0コメント