Glossary of Terms

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Active Amplifier Loads
Active amplifier loads are devices connected to the output of an amplifier which are capable of returning energy into the output of an amplifier from external sources.  An example of such a device is a piezoelectric transducer, which will develop and deliver energy into an amplifier’s output when expanded or contracted due to an externally applied force. 

Amplifier Input Signal (differential configuration)
A particular low noise connection technique employed between an amplifiers’ input stage and external signal sources consisting of three (3) conductors.  The signal to be amplified appears as a difference signal between two (2) of the conductors [A and B] in reference to the third conductor [C], acting as a reference.  Noise signals commonly appearing on both signal lines [A and B] will not be amplified.   

Amplifier Input Signal (inverting configuration)
An amplifiers’ input stage connection which receives signals to be amplified over a single conductor [A], in reference to common ground [B], whereby the amplified signal at the amplifier output is in an 180 degree phase relationship (inverted) to the inputs’ received signal.  

Amplifier Input Signal (non-inverting configuration)
An amplifiers’ input stage connection which receives signals to be amplified over a single conductor [A], in reference to common ground [B], whereby the amplified signal at the amplifier output is zero (0) degree phase relationship (non-inverted) to the inputs’ received signal.

Automatic Power Limit 
A circuit function which measures and limits the internal power dissipation within an amplifier or power supply. This feature prevents overheating within the amplifier that could occur due to improper loading and is used on most Trek power amplifiers.

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Back Light Saver
A feature which automatically provides a time related turn-off or turn-down mode for the LCD’s (Liquid Crystal Display) back lighting element to conserve battery life on battery operated instruments such as the Trek Charged-Plate Monitor models.

Balance Tests (Float Tests) 
Charged-Plate Ionization Monitoring instruments, such as Trek Models 156A, 157, & 158, employ a mode to allow determination of the relative quantities of positive and negative air ion (ion balance) being emitted from an air ionizer.  For this purpose, the charge monitor sensor plate is allowed to freely float in the air ion field to an ion generated voltage level to indicate the voltage to which objects placed in the ion field will be driven to by the discharger. 

Bandwidth (Large Signal)
The frequency at which the output sine wave amplitude of an amplifier or other circuit departs from linear behavior (normally a 1% distortion value is chosen as the point of departure) when producing full output voltage capability. The Large Signal Bandwidth should be expressed as a range of sine wave frequencies. Example: DC to 3 kHz.

Bandwidth (Small Signal)
The frequency at which the output sine wave amplitude of an amplifier or other circuit falls to 70% (-3 dB) of the low frequency value (close to DC) given a constant amplitude input signal. The Small Signal Bandwidth should be expressed as a range of sine wave frequencies. Example: DC to 30 kHz.

Bar Code Wand
Normally a hand-held device used for optically scanning bar codes for the purpose of ionizer or other product identification when filing ionizer performance or other product tests results. For example, the Model 157 interfaces with a bar code wand to provide a capability of storing hundreds of ionizer test results for later evaluation.   

Battery Charger / Eliminator 
A power supply module (line cube) which allows simultaneous equipment operation and battery charging of battery operated equipment from a line supply.  For proper operation the equipment must be designed to accept operation from a battery charger/eliminator.

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Capacitive Loads
Amplifier or power supply loads which represent, primarily, a capacitive reactance.  In AC applications, capacitive loads require current to be added and subtracted from the capacitance over time.  This can be achieved using amplifiers which feature multiple quadrant output capability (ie: the ability to source or sink current in and out of the capacitive load over the voltage range desired.)  All Trek high power amplifiers feature multiple quadrant operation capability to provide fast response capacitive load operation.

CE Compliance 
CE Compliance refers to the operation of electrical equipment being within the standards proscribed by the European Council (E.C.).  Most Trek products comply with these standards denoted by the “CE” symbol appearing on those products. 

Compliance Statement (Declaration of Conformity)
A certificate which attests to the compliance of a particular Trek product to the CE standards provided by the European Council.

Current (loop) Output
An industrial standard type current output used for remote monitoring of the measurements made by instruments which is relatively independent of the length of lines between the measurement device and the central monitoring remote location. The most popular range described by the standard is a 4 mA to 20 mA output current range.

Current Monitor
A buffered voltage output providing a representation of the load current of an amplifier or power supply. Trek provides a current monitor for most amplifiers and supplies.

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Denotes the ability to measure or reproduce a signal’s DC value (as well as its AC value) with accuracy which is not time dependent. All Trek power amplifiers are DC stable.

Decay Tests (Discharge Tests)
Charged-Plate Ionization Monitoring Instruments such as the Trek Models 156A and 157 employ a “decay test” mode to allow determination of the absolute quantities of positive and negative air ions impinging on the charged-plate sensor.  This mode, used independently for positive and negative air ion testing, allows pre-charging of the charged-plate sensor to a predetermined “start” voltage value and then meaning the time required for the air ions to discharge the sensor to a predetermined “stop” voltage value.     

Declaration of Conformity (Compliance Statement)
A certificate which attests to the compliance of a particular Trek product to the CE standards. 

Differential Input  
See “Amplifier Input Signal (differential configuration)”.

Digital Enable     
Many Trek measurement and control products (amplifiers and supplies) feature remote turn-on capability from remote locations through a “Digital Enable” function.  The Digital Enable function is normally connected to the remote location by a BNC connector cable using TTL logic level signals.

Discharge Tests
See “Decay Tests”  

Digital Panel Meter

Dual Unit (Trek Models 601C, 603, PZD350A, PZD700A) 
Many Trek measurement and control instruments (amplifiers and supplies) are available in multiple channel designs which allow two (or more) channels of measurement or control in a single enclosure which can be rack mounted and operated from a single supply line.

Dynamics Adjust (Dynamic Adjustments)  
In many Trek power amplifiers, a graduated one-turn potentiometer (sometimes two potentiometers) is used to optimize the AC response of an amplifier over a wide range of load parameters.

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The branch of electrical science which deals with the properties and effects of electricity at rest, or static electricity. TREK, INC. is a recognized world leader in the measurement and control of electrostatic quantities.

Electrostatic Charge Monitoring
The use of specific measuring devices which are sensitive to the electrostatic field as generated by electrostatic charge so as to quantify the charge magnitude without affecting the charge itself. TREK, INC., being a world leader in electrostatic charge monitoring, provides many instruments and systems which accurately measure electrostatic fields and thereby measure electrostatic charge using a non-contacting probe sensor technique. In addition, contacting type electrostatic charge measurement equipment has been introduced by Trek in 2005 [please refer to “Electrostatic Voltmeter” (Trek Model 800)].

Electrostatic Voltage (EMF)  
A quantity of force existing between two (2) points [A and B], as measured by the amount of energy required to move a unit of charge (q) between points [A and B].

Electrostatic Voltmeter (ESVM)
An instrument that measures electrostatic voltage without charge transfer is called an electrostatic voltmeter.  A primary characteristic of an electrostatic voltmeter is that it accurately measures surface potential (voltage) on any kind of material without physical contact and therefore, no charge transfer and loading of the measured source can occur. Recently, Trek developed the Model 800 (Infinitron®) ultra high impedance voltmeter which can perform contacting measurements virtually without charge transfer. 

Electrical overstress

Electrostatic Discharge

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Fault Status
A FAULT STATUS indicator will illuminate or (typically) a TTL low output is generated when high-voltage output of an amplifier is disabled due to one of the following situations:  the set current trip level is exceeded, an internal power supply fault is detected, or the internal interlock circuit is interrupted such as when the top cover is removed.

Float Tests
See “Balance Tests”

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Gain (DC voltage gain)
The scale of the output voltage span to the input voltage span of an amplifier usually expressed in volts per volt. Example:1000 V/V.

(1) A conducting connection, whether intentional or accidental between an electrical circuit or equipment and the earth, or to some conducting body that serves in place of earth. (2) The position or portion of an electrical current at zero potential with respect to the earth. (3) A conducting body used as a return path for electric currents and as an arbitrary zero reference point.

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IEEE – 488 (Trek Model 668B Power Supply and Model 370 Electrostatic Voltmeter)
The Data Acquisition Modules contain programmable capabilities for use with the General Purpose Interface Bus (GPIB) as defined by the IEEE Standard 488.2-1978.  With the Data Acquisition Module, the Trek unit can become part of an automated instrumentation system and be under complete, interactive control from a remote bus controller. 

ION Plate Collector
The sensor portion of the charged-plate monitoring system which is placed into the measurement field. The patented Trek ion collection plate design allows plate charging (see “Decay Tests”) and ion field monitoring through the same coax cable. 

Impedance is the complex sum of DC RESISTANCE and AC REACTANCE and is symbolized by the letter “Z” with the unit “Ω”.  If an AC signal is applied to a circuit containing AC reactive components, the phase of the resulting current need not be the same as the phase of the output voltage. The relationship between voltage (complex voltage) and current (complex current) cannot therefore be described by a scalar quantity such as resistance, as is the case for pure resistance DC circuits. A two-part quantity such as vector (or complex number) is needed, and this quantity is termed complex impedance. 

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Liquid crystal display

Light emitting diode

Limit (Current Limit / Current Trip)
For Trek Amplifiers, a graduated potentiometer is typically used to adjust the current limit value of an amplifier to prevent amplifier overloading.  Some Trek amplifier models have a switch to select for either current limit (limits current/reduces voltage) or current trip (disables HV output).  For example: the Model 10/40A has a current limit feature that is adjustable for 0 to 40 mA using the CURRENT LIMIT/TRIP ADJUST potentiometer on the front panel.  When in the current “limit” mode, the Model 10/40A’s OUT OF REGULATION STATUS indicator will illuminate and the OUT OF REGULATION STATUS output will provide a TTL low.  If the Model 10/40A remains in a current limit for more than 500 ms, the FAULT/TRIP STATUS output will provide a TTL low. When in the current “trip” mode, the high-voltage output will shut down upon the output reaching the set current trip value. 

Load Compensation Adjustments 
The Dynamics Adjust potentiometer on Trek’s amplifier panel is adjusted to optimize the AC response characteristics of the output voltage waveform when using a capacitive load device or when changing load devices with different capacitive values.  For example: adjusting the Dynamics Adjust potentiometer will optimize the AC response for a square wave.  Turning this potentiometer clockwise or counter-clockwise will decrease or increase damping to minimize voltage spikes and distortion, allowing a more perfectly formed amplified waveform with a particular load.

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Null Voltage Source (Model 320C Electrostatic Voltmeter)
A calibrated 10-turn dial represents a 10 volt supply, with switch selectable polarity, which is used to produce zero volts output when the electrostatic voltmeter probe is coupled to a known zero volt surface.  This feature is also used to null contact potentials associated with measured surfaces in reference to the Model 320C probe’s gold plated sensing electrode.  

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Oscilloscope [Cathode-Ray Oscilloscope (CRO)]
 A measurement instrument used to measure the characteristics of periodic or single event waveforms such as wave shape, frequency amplitude, duration, etc.

Out of Regulation
Most Trek Amplifiers have an indicator which will illuminate when the amplifier fails to produce the required high-voltage output such as during current limit or short circuit load conditions. Some Trek amplifiers have a BNC connector output that will provide a TTL signal to indicate an ‘out of regulation’ status for external signaling purposes.

Output Noise 
Undesired signals at an amplifier's output that are not related to the input voltage. The Output Noise is normally expressed as a voltage limit value over some frequency range. Trek amplifier technology provides very low noise levels.

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(1) A prevalence of electric charges, either positive or negative.  (2) a magnetic direction (3) a method for connection of certain components, for example electrolytic capacitors, intended to avoid improper operation.   

Probe (Spatial Resolution Characteristics)
Describes the dimensional characteristic of a non-contacting ESVM probe sensor in performing measurements of a specific area on a measured surface to a specified accuracy at a specified distance.

Probe (Sensitivity Characteristic)
Describes the useful minimum voltage level a particular Trek probe sensor (and its base assembly unit) can resolve under specific bandwidth capability. For example, the Trek Model PD1216P high sensitivity probe sensor (with the Model 325 base assembly unit) can resolve 1 mV voltage levels at a spacing of 0.4 mm.

Probe (Speed Characteristic)
Describes the useful maximum measurement speed a particular Trek probe sensor (and its base assembly unit) can be used at to perform surface voltage measurements.  The speed is specified as the ‘speed of response’ or slew rate (volts per unit time) in response to a step input to changes in measured voltage. For example, Trek Model 3800E-2 probe sensor (with the Model 370 base assembly unit) has a speed of response (slew rate) of 50 V/us.

Probe (Temperature Characteristic)
Describes the range of operating temperatures for Trek probe sensors. Many Trek probe designs are available for high temperature operation up to 100 degrees Celsius while the normally specified range is between 0 to 60 degrees Celsius.

Probe (Transparency)
Trek offers a transparent probe series, to perform electrostatic voltage measurement while radiating a surface (for example, with light). Also performs ‘time of flight’ measurements for charges associated with electrophotographic surfaces. The Trek Model 3629A probe operates with the Trek Model 370TR High-Speed Electrostatic Voltmeter.  Using the Model 3629A probe sensor, the user may direct light through the same aperture which makes the electrostatic measurement. The illuminated area of the surface is typically slightly larger than the measured area in order to eliminate electrostatic fringing effects.

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Reference Supply
A regulated electronic power supply. Trek reference supplies feature high-temperature and time stability outputs and can be used as a secondary traceable standard.   

A circuit that can maintain a constant value of either voltage or current under a wide range of operating conditions 

Remote On/Off
A TTL compatible signal is used to externally turn ON or OFF the high-voltage for amplifiers or the internal high-voltage power supplies associated with Trek electrostatic voltmeters.

The ratio of DC voltage applied to the resulting DC current. The symbol for resistance is “R” and the unit is Ω. The inverse of resistance is conductance. The Trek 152 Resistance/Volume Meter measures resistance characteristics of surfaces using applicable standards using different probe designs such as point-to-point probes, concentric ring probes, and ‘pencil’ probes.

Measurement of the amount of resistance of a material and is independent of the dimensions of the sample of the material. The Model 152 Meter has a variety of measuring probe electrode configurations are available for making surface resistance measurements, volume resistance measurements or used for surface resistivity calculations.

Response Speed Control (Trek ESVM Models 320C, 323, 325)
Trek electrostatic voltmeter models normally use a control to adjust the gain of the probe to optimize the AC response of the system.

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Sampling (modulation systems)
The process of obtaining a sequence of instantaneous values of a wave or signal at regular or intermittent intervals 

Sampling (pulse terms)
A process in which strobing pulses yield signals which are proportional to the magnitude (typically a function of time) of a second pulse or other event

Slew Rate
Slew rate describes the maximum rate of change of the voltage output of an amplifier in response to a step change input signal.  The Slew Rate is typically measured by Trek during the 10% to 90% interval of the output step and is expressed as being greater than a given value such as, “greater than 100 V/μs”.

Speed of Response
For electrostatic voltmeters: the rise time or fall time of the voltage measurement in response to a specified step change in the measured voltage. The speed of response is expressed as a period of time for a specified input step change and it is expressed as a limit value. For example, “less than 10 ms for a 2 kV step change”.  The speed of response is specified for a specific set of ideal conditions, such as at a certain probe-to-surface spacing.

Status Indicators
Colored LEDs which represent amplifier conditions.  Trek amplifier models normally include indicators for HIGH-VOLTAGE ON, OUT OF REGULATION, OVERLOAD, CURRENT TRIP, CURRENT LIMIT, COMPLIANCE, and others.

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Transconductance Amplifier 
A transconductance amplifier responds to an externally applied input voltage signal by producing a proportional output current. Some Trek high-voltage amplifier models are available with a transconductance operation mode. 

Trip (Current Trip/Trip Status) 
See “Limit” (Current Limit)

TTL (Transistor-Transistor Logic) Signals
A standardized digital signal level format describing the voltage levels associated with a digital low [0] and a digital high [I] levels. Trek amplifiers and measurement instruments which interface with external digital signals use the TTL format.

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Voltage Monitor 
A buffered output voltage providing a low-voltage replica of the high-voltage output of an amplifier at a given scale factor. Most all Trek amplifiers provide a voltage monitor.

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WAVE Software (Model 158 Charged-Plate Monitor)
The PC software which operates the Model 158 Charged-Plate Monitor

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Zero Adjust  
A control, either manual or automatic, used to control the output voltage or signal level of Trek amplifiers and/or electrostatic measuring equipment when applying a zero level to the input.

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