The Giga Meter is another device created to detect ethereal energies. Specifically, it measures psychomagnotheric energy in Giga Electron Volts, which are the standard unit of measurement for high-energy physics.
It appears as a hand-held black unit, with a large sensor 'dome' mounted to the front underside at a slight angle. Above this, two electronic probes sway back and forth, presumably to pick up or filter out energy.
It was shown to be kept in a silvery carrying case. 
Around the time the Ghostbusters' dissolution after the Gozer incident, Egon Spengler and Ray Stantz, were working on a theory that the human emotional state has a measurable effect on the psychomagnotheric energy field.  Egon continued to gather data on this theory while he was employed at the Institute for Advanced Theoretical Research. The theory and research culminated in the invention of the Giga Meter.
The Giga Meter was only used briefly, in response to the Psychomagnotheric Slime discovered below the streets of New York. While investigating Dana Barrett's apartment and First Avenue, Doctors Spengler and Stantz used the Giga Meter in conjunction with the original P.K.E. Meter. While the P.K.E. Meter can act as a psychokinetic dowsing rod, the Giga Meter more likely serves as a measuring instrument, for recording the exact levels of psychomagnotheric energy generated by an entity in a measurable unit. For instance, when used to gauge the Psychomagnotheric Slime, the Giga Meter had a reading of 2.5 Giga Electron Volts whereas the P.K.E. Meter measured 1118.
The Giga Meter was not used during the Shandor Incident; because the primary slime that is utilized, Black Slime, is supersaturated with negative energy and not psychomagnotheric energy. It was not similar enough to warrant the Giga Meter's use.
Egon used a Giga Meter to take an initial scan of Fantastic Land once the Ghostbusters entered the grounds. Months later, in November, Egon ran a sweep of Herald Square with the Giga Meter after Death, Eugene Visitor, and the Megaspook vanished. Kylie Griffin used a Giga Meter to track Gareth Dibello throughout Central Park. The meter was able to pinpoint him 150 yards away at Bridge #24. Egon brought the Giga Meter along on the investigation of the gravitational anomalies that manifested on Columbus Circle.
While in Venice for a couple hours, Ray attempted to establish a baseline for psychokinetic activity in preparation for their case on Poveglia. He took readings with a Giga Meter but was surprised he buried the needle due to the abundance of benign ghosts in the area. Ray tuned the meter to compensate for and sift through the heavy local concentration of P.K.E. in order to track entities on Poveglia. The adjustment aided the Ghostbusters in detection of the Plague Doctor Ghost, the biggest individual reading on the island. After entering the asylum, Ray picked up a double reading, a second layer of data. In a basement, he discovered the source of the stronger reading - the Poveglian Artifact. However, the ghost reappeared behind him and the meter registered a "88.0" reading. After the ghost was trapped, Ray observed they drastically reduced the local psychokinetic energy but it soon recovered at an exponential rate. The meter's dome sustained irreparable damage when Kaia May released the Unknown Soldier Ghosts in a Paris police station while in search of the Poveglian Artifact.
Contradictions in AppearanceEdit
It is unknown why but in some promotional materials, such as the Puzzle Book and Coloring Book, the Giga Meter instead is portrayed as a box like device.
- In the Ghostbusters II August 5, 1988 draft, the Giga Meter is used. Instead of Ray, it is the Giga Meter that is lowered down the hole they make. The readings are so strong, the meter is half-melted and fried to a crisp.   
- In the Ghostbusters II August 5, 1988 draft, the Giga Meter reads 3 GeVs of psychomagnetic force off a normal human. 
- On page 23 of the February 27, 1989 draft of the Ghostbusters II script , Ray Stantz reveals he and Egon Spengler "have been working on a gauge to measure psychomagnotheric energy in GEVs - giga electron volts."
- In Ghostbusters Issue #2 page 19, baby Egon's toy is a Giga meter.
- Ongoing Series
- Volume One
- Volume Two
- Volume Three
- ↑ The Giga meter carrying case (1989). Ghostbusters II (1989) (DVD ts. 21:50-22:03). Columbia Pictures.
- ↑ 2/27/89 script, Page 14 via Spook Central
- ↑ Aykroyd, Dan & Ramis, Harold (1988). Ghostbusters II (August 5, 1988 Draft) (Script p. 26). Ray Stantz says: "Egon and I have been working on it. It measures psychomagnetic energy in GeVs--giga-electron-volts."
- ↑ Aykroyd, Dan & Ramis, Harold (1988). Ghostbusters II (August 5, 1988 Draft) (Script p. 29). Paragraph reads: "They lower the gigameter into the hole on a very long line."
- ↑ Aykroyd, Dan & Ramis, Harold (1988). Ghostbusters II (August 5, 1988 Draft) (Script p. 29). Paragraph reads: "There is a bright flash deep down the hole. They quickly pull up the line and gape at the gigameter, which is half-melted and fried to a crisp."
- ↑ Aykroyd, Dan & Ramis, Harold (1988). Ghostbusters II (August 5, 1988 Draft) (Script p. 74). Egon Spengler says: "You're reading three at the moment. That's normal. The different between 3 and 130 in terms of potential volatility is like the difference between a firecracker and a stick of dynamite."
- ↑ 2/27/89 script, Page 23 via Spook Central