Custom Meter Faces

A Pictorial Instruction

I recently had the need for a number of analog meters to complete a project in progress. I quickly found that these meters can be expensive! However, I also found there are reasonably priced surplus meters available if you don't mind doing a little work to get them to suit your purpose. However, As an added bonus for your efforts, you get a one of a kind custom meter. In the event you have not had the opportunity to modify a surplus meter before, I will provide a step by step pictorial instructional diagram. Mind you the need to customize a meter is certainly not a new idea. You can read and learn about the process in many ARRL publications going back quite a few years however, with a computer the mechanics of the process has changed a bit, and allows a person to be quite creative with the process.

This is the meter as purchased. If you are interested, these were purchased from All Electronics (Standard, "Not affiliated" disclaimers) for [email protected] $1.25 each, which I thought to be very reasonable for a meter of this quality. It measures approximately 1.25" x 1.25". It is a 250ua movement.

The first thing you must do is decide what you want your meter to do. In this case, the purpose was to use them as simple volt meter, which requires nothing more than inserting an appropriate resistor in series with the meter. It is necesary to mark or take notes as to where the applied measured voltage reads on your un-modified meter dial, For example; with a 660K resistor in series with the meter leads, the meter will read 135 volts full scale. If you will be using the meter for current measurements, you will need to insert a meter shunt of a low resistance value. Click here for more information on creating a meter shunt. Otherwise, Most Electronic Handbooks will give you specific details in making these shunts.

The first mechanical step is to remove the meter housing. Most meters are held together with nothing more than scotch tape making it a simple matter to cut through the tape with a sharp razor knife. In all of these procedures, work carefully and patiently as the meter mechanisms are delicate and will not suffer through abuse. Be aware that many times they can be stubborn and will fly apart with the slightest provocation. I am quite experienced with this phenomona!
Open the meter carefully. I chose not to remove the cover completely. This allows you to re-cover the meter after removing the face plate, keeping dust and other air borne particles from getting into the meter mechanism.
The next step requires a gentle hand. You need to remove the face plate from the meter housing. Unfortunately, the plates are glued to the plastic casing. If you attempt to pry the plate off, you will either bend the plate, or damage the very delicate needle mechanism of the meter. Freeze spray makes it into an easy process. Using a very light spray, freeze the metal plate causing the underlying glue to separate from the plastic. On these meters, there is a very distinctive cracking sound as the separation occurs. The meter plate will very literally fall out of the housing. With stubborn plates, a very light pry with your razor knife will supply extra motivation for it to slide off. Be carefull not to get any of the spray on your plastic meter bezel, as the chemicals in the freeze spray will cause a distortion in the plastic.
The next step requires that you import the image of the meter face to your graphics program. The easiest way to do this is with a desk top scanner. Scanners have become extraordinarily reasonably priced. The one I use cost $39.95 after rebate. If you anticipate working on many home brew projects, it is probably worthy of your consideration. Otherwise you will need to measure the plate as accurately as possible and electronically re-create the face plate in your program. I have become very accustomed to working in Paint Shop Pro, available as a free 60 day trial on their web site. The screen shots to follow are directly from this program.
This is an actual screen shot of the scanned face plate image. I try to scan at the maximum resolution that I have the patience to use. Extremely high resolutions take enormous processing times for each manipulation, much like the TV commercial showing the process time of a fast ball. I used 2400 dpi for these images. The higher the resolution, the sharper the final printed image will be, up to the limits of your printer. As you can see, the scanner picks up (and adds) many imperfections to the meter plate. Before working with the image, I usually "clean" the image.
The process starts by selecting all of the bright areas of the image, using the "Magic Wand" in Paint Shop Pro (PSP). This tool allows you to select certain areas of the image for processing without affecting the remainder of the image. Here, I have selected the bright areas of the image and then used the invert tool to select everything BUT the bright areas of the image. Be sure to select the confined areas within "Zero's" and "R's", etc.
Once these areas are selected, simply "cut" them from the image. In PSP, this automatically places the cut image on the clipboard, which then allows it to be used at a later time. Then De-select all areas of the image, and clear the image which places a pure white backgound on the workspace. In essence, you have just created a pure white work space :-). The advantage in going to this extra effort to create a white work space is that you have the usable portion of your image "Saved" on the clipboard, ready for re-insertion. In addition, all of the original image proportions are maintained.

Here is a comparison of the original scanned image, to the processed image on the right. Later, you will paint over the extraneous lines on the top and sides with a white paint brush.

Next, eliminate all of the areas of the original meter that you do not want. In PSP, using the "Magic Wand" again makes the process easy. To eliminate the Red, Yellow and Blue, use the "RGB" values option within the Magic Wand, and then delete each color in turn. Use a white paint brush to paint over the numbers that you do not need. From here, what you need in a meter is of your own design and I can only offer the advice of patience and experimentation to get exactly what you want in a custom meter.

I chose a very simple design for these meters, so as to compliment the rig for which they are intended. I used a coarse brown spray tool to develop a texture to the meter. The last step is to glue the printed face plate on top of the original face plate, then trim to fit with a razor knife..
Here is the final result. As you can see, I chose a fairly plain and simple face for this project however, there is nothing to limit your creativity!

This a picture of the completed power supply. The Suppy is intended to power Glowbug, or Tube Type Qrp Rigs. For more pictures of this rig, Click Here.

Have Fun!

KD6CC

KR6LP - Lake Perris Qrp Society

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