Monroe Electronics 284 User Manual

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Operators’ Manual
Monroe Electronics, Inc.
Model 284
NanoCoulomb Meter
P/N 0340117
284-1/100
100 Housel Ave  PO Box 535 Lyndonv il le NY 14098 1-800-821-6001 585-765-2254  fax: 585-765-9330 monroe-electronics.co
Section 1

SPECIFICATIONS:

Display: ½” x 3½ digit LCD Standard Ranges:
Range: Resolution:
200nC 0.1nC 20nC 0.01nC

Optional Ranges Available:

Range: Resolution:
2000nC 1.0nC
2.0nC 0.001nC
Accuracy: 2% Output: 0 to ±2 volt analog, 1k Drift: 0.1pC/sec. Typical Battery: 9 volt Eveready #216 or equivalent NEDA #1604.
Battery life over 400 hours.
1
Dimensions: 6” x 3½” x 2
/8” (150mm x 90mm x 54mm)
Weight: 8½ oz. (0.24 kg) with battery

Compatible accessory probes:

Faraday Cup, Model 284/22A:
Outer dimensions (nominal)— 3½” dia. x 5¾” tall Inner dimensions (nominal)—
5
/8” dia. x 2¾” deep
2
Faraday Cup, Model 284/22B:
Outer dimensions (nominal)— 8” dia. x 10” tall Inner dimensions (nominal)— 6” dia. x 6¾” deep
Faraday Cups are equipped with BNC connectors and furnished with 3­foot mating cable to connect t o Model 284 instrum ent . Can be used to measure powders and liquids as well as solid objects.
Point contact probe:
Various—contact factory
Page 1 284.CBSM-12/98-RCA
Section 2
GENERAL INFORMATION
The Monroe Electronics Model 284 Nanocoulomb Meter is a convenient battery powered portable instrument for direct measurement of charge in t he r ange between 1 picocoulomb (limit of resolution) and 2 micr ocoulom bs ( maximum displayable value). The standard instrument conf iguration provides two ranges— ±19.99nC and ±199.9nC—with one-decade extension in either direction available as a factory option at time of or der or as an aftermark et upgrade.
The NanoCoulomb Meter charge amplifier consists of an I.C. electrometer amplifier with a high quality capacitor connect ed in the negative feedback position. The input terminal (center pin of a BNC connector) f eeds the inverting input of the amplifier through a current limiting resistor. This inverting input is at zero volts or virtual ground so all charge that is induced or directly deposited at the input terminal is transf er red to the integrating capacit or. Since Q=CV, the output voltage of the charge amplifier is directly proportional t o t he charge injected in the input, that is, for a 0.1µF integrating capacit or , a +100 nanocoulomb input equals 1.0 volt at the output . The input being at virtual ground reduces leakages and polarization of insulators, thus minimizing these effects on the reading s.
The NanoCoulomb meter is zeroed by a low leakage momentar y contact switch, which discharges the integrator. A built-in reference quality voltag e split ter corrects for all offsets.
The electrometer is followed by a scaled-gain inverter , which is used to correct the gain error caused by variations in capacitors and the inversion of the input amplifier and to drive the 3½ digit Liquid Crystal Display (LCD) and the analog output circuit.
The readout is thus always expressed directly in nanocoulombs with the decimal point properly placed and the output is always 2 volts for full scale, regardless of range.
In order to be fully functional, the Model 284 requires some sort of input sour ce device. Two types of input devices are readily available from Monroe Electronics as accessories to the Model 284—Faraday cups and contact probes.
The Faraday cup consists of two concentric cans with expanded polyethylene as an insulator between them. The outer can is at ground potential and the inner can is the sensing electrode for t he elect r ometer. These are available in two standard sizes or may be custom designed to order.
The point contact probe is held in a manner similar t o which one would hold a pen or pencil and is used to make charge measurem ent s by direct cont act with small objects or small areas of objects such as individual pins on IC’s.
11
Any input device used must have low leakage (>10
) and provide an electrical
reference (usually earth ground) .
Page 2 284.CBSM-12/98-RCA
Section 3
OPERATION
The Monroe Electronics Model 284 Nanocoulomb Meter has been designed for extreme ease of operation.
1. Connect Faraday cup to Model 284.
2. Switch power on.
3. Set to least sensitive range (decimal point furthest to the rig ht for your
instrument).
4. Zero the instrument.
5. Place charged object in cup and take reading.
The Faraday cup comes with a cover, which can be used when zeroing or when taking readings in areas where one suspects that out side electric fields may be affecting readings.
One can measure both “mobile” and “immobile” char ge in objects to be tested. To do this, follow the above procedure. Af ter step 5, note the reading (this reading is the “total” charge reading). Then remove the object being tested by dumping it out of the cup or by lifting it out with a set of wooden tongs. The reading that is now being displayed in the meter is the “ m obile” char ge on the object being tested.
Since “total” charge = “mobile” char ge + “immobile” charge, we can calculate the “immobile” charge by subtracting the “mobile” charge fr om the “total” charge.
Page 3 284.CBSM-12/98-RCA
Section 4
CALIBRATION CHECK
The purpose of this section is to provide the oper at or of the Monroe Electronics Model 284 Nanocoulomb Meter with a means of verifying that overall calibration of the instrument is within the specified limits (±2%).
Method 1: Procure a calibration capacitor. It should be a polystyrene or polypropylene
capacitor with a precisely known value of approximately 10nF (0.01µF) (Mallory SX-110 or equivalent).
With the capacit or charged to exactly 1.00 volt and then discharged directly into the input terminal (BNC connector) or between the inner and outer parts of the Faraday cup, a meter reading equal to t he capacitor value (±2%) should appear on the Digital Panel Meter (DPM) set to the 20-nCoulomb range.
Charging the calibration capacitor t o 10.00 volts and then discharging it into the input should produce a DPM reading of ten times the capacit or value (± 2%) on the 200-nCoulomb range.
It is important to handle the calibr ation capacitor very carefully. Do not
hold the capacitor by its body or discharge it by touching both leads with the f ingers. Hold the capacitor by one lead only
. Use a clip-lead connected between the GND jack and this lead of the capacitor to maneuver t he ot her lead of the capacitor between the “hot” side of the charging source and the input terminal.
Method 2: Use a secondary standard charge source such as a Keithley Model 263
Calibrator/Source, following manufacturer’s instructions. Incorrect DPM readings indicate a need for calibr ation.
Page 4 284.CBSM-12/98-RCA
WARRANTY
Monroe Electronics, Inc., warrants to the Owners , this instrument to be fr ee from defects in material and workmanship f or a period of two years after shipm ent from the factor y. This warranty is applicable to the original purchaser only.
Liability under this warranty is limited to service, adjus tment or replac ement of def ective parts (other than tubes, fuses or batteries) on any instrument or sub-assembly returned to the factory for this purpose, transportation prepaid.
This warranty does not apply to instruments or s ub-assemblies subjected to abuse, abnorm al operating conditions, or unauthorized repair or modification.
Since Monroe Electronics, Inc. has no control over c onditions of use, no warranty is made or implied as to the suitability of our product for the customer’s intended use.
THIS WARRANTY SET FORTH IN THIS ARTICLE IS EXCLUSIVE AND IN LIEU OF ALL OTHER WARRANTIES AND REPRESENTATIONS, EXPRESS, IMPLIED OR STATUTORY INCLUDING BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. Except for obligations expressly undertaken by Monroe Electronics, in this Warranty, Owner hereby waives and releases all rights, claims and remedies with respect to any and all guarantees, express, implied, or statutory (including without limitation, the im plied warranties of m erchantability and fitness), and including but without being limited to any obligation of Monroe Electronics with respect to incidental or consequential damages, or damages for loss of use. No agreement or understanding varying or extending the warranty will be binding upon Monroe Electronics unless in writing signed by a duly authorized representative of Monroe Electronics.
In the event of a breach of the foregoing warr anty, the liability of Monroe Electronics shall be limited to repairing or replacing the non-conforming goods and/or defective work, and in accordance with the foregoing, Monroe Electronics shall not be liable for any other damages, either direct or consequential.
RETURN POLICIES AND PROCEDURES
FACTORY REPAIR:
Return authorization is required for factor y repair work. Material being returned to the factory for repair must have a Return Material Authorization number. To obtain an RMA num ber, call 716-765-2254 and ask for Customer Service.
Material returned to the factory for warranty repair must be acc ompanied by a copy of a dated invoice or bill of sale, which serves as a proof of purchase for the material.
Repairs will be returned promptly. Repairs are normally returned to the customer by UPS within ten working days after receipt by Monroe Electronics, Inc. Retur n (to the custom er) UPS charges will be paid by Monroe Electronics on warranty work. Return (to the customer) UPS charges will be prepaid and added to invoice for out-of-warranty repair work.
EXPEDITED FACTORY REPAIR:
All material returned to the fac tory by air or by an overnight service will be expedited. Expedited factory repairs will be returned to the custom er by the same mode of transportation by which the material was returned to the factory for repair (i.e., material returned to the factory by an overnight service will be returned to the customer by an overnight service).
NOTE: Return (to the customer ) transportation expenses for expedited factory repairs will always be at the expense of the customer despite the warranty status of the equipment.
FACTORY REPAIRS TO MODIFIED EQUIPMENT:
Material returned to the f actory for repair that has been modified will be not tested unless the natur e and purpose of the modification is understood by us and does not render the equipment untestable at our repair facility. W e will reser ve the right to deny service to any modified equipment returned to the f actory for repair regardless of the warranty status of the equipment.
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