Panel meters were invented by a French physicist, Jacques-Arsène d’Arsonval in the late 1800′s. His invention of the moving coil meter movement or galvanometer is the foundation for today’s meter movements. Even though the actual fabrication of meters can vary significantly, the basic underlying technology still relies on D’Arsonval’s invention.
Meters are commonly found on audio equipment and in a wide variety of industrial environments. Even though analog meters provide cool looking moving parts, many applications today are changing to more accurate and faster acting digital panel meters which use led displays or Liquid Crystal displays.
DPM’s (Digital Panel Meters) are often selected for faster response and better accuracy. Also, they can now be obtained at prices that may be less than a good analog panel meter. Digital Panel Meters also have better linearity than most of the analog meters so a DPM offers some real benefits over an analog panel meter. A typical Digital Panel Meter has a 200mV sensitivity rating (199.9mV full scale) so they are comparable to analog meters in terms of voltage drop for current measurement. A Digital Panel Meter usually is rated at 100Mohm input impedance. This means voltage loading is extremely low. Also, most Digital Panel Meters will measure positive and negative voltage or current.
Most DPM’s are designed with 3 1/2 digits. This digit capacity allows them to display up to a maximum of 199.9mV. The digit to the left can only be blank or 1, and the other “half” is used to display a negative sign to show that the input is negative as it relates to the ground or common terminal. This frequently results in a situation where some of the range is wasted if the user wants to display a range other than 0 to 1999. Also, most Digital Panel Meters do not select the decimal point automaticly. The end user may do so using extra pins provided for this purpose or he may choose to just ignore it depending on his desired results.
Wayne Thorpe, President