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This catalog supersedes all other Instruments Inc. documentation. A price sheet is available upon request. Some units may not be available for export to all countries. Instruments, Inc. is responsible for obtaining an export license for each sale. Please contact the factory concerning your needs. Specifications and prices are subject to change without notice.


Switching Amplifiers

Stair-Step Modulation

Class SS modulation synthesizes the desired output by sequentially switching full bridge outputs on and off at the signal frequency.

Since the output transistors turn on only once each cycle, this modulation is used when the maximum output frequency is desired. Each bridge contributes one step to each polarity of the output waveform. The outputs of each bridge, which are in series, are held in a low impedance state until called upon to contribute to the sum. The distortion decreases inversely with the number of Output PWBs used. The distortion for a 4 bridge Class SS amplifier is about 10% at full output.

Amplitude, frequency, and phase can be closely and rapidly controlled, but amplitude modulation results in increased distortion, since lowering the amplitude means using fewer steps. Power supply modulation, although slow, may be used to control output amplitude without increasing distortion.

Class SS modulation is well suited for high power applications where distortion is not a problem. As the power rating increases, more Output PWBs are used which reduces the relative size of each step and improves the waveform.

Pulse Width Modulation

PWM requires that the output transistors switch at 4 to 10 times the maximum signal frequency. Amplifiers using this technique and voltage feedback have 60 dB of dynamic range and distortion of less than 0.2%. Current feedback can be used to synthesize a resistive output impedance. This impedance is also known as damping factor and may be made as great as twice the matching load impedance at low frequencies.

A PWM amplifier may be used to reproduce arbitrary waveforms. It comes close to the performance of a linear amplifier with higher efficiency. Generally, the total losses in the output stage are less than 10% of the output VA and the overall efficiency including power supply and transformers is at least 75%.

High power amplifiers, which use multiple Output PWBs, offer improved performance by using a polyphase carrier modulation technique to cancel ripple components. The output includes the amplified input signal plus sidebands around harmonics of the switching frequency. A good general purpose filter will allow full power into a resistive load up to 1/4 of the switching frequency. Capacitive loads will lower the filter frequency and absorb much of the switching harmonic current. Inductive loads will raise the filter frequency and reduce the high frequency output. In some applications, no output filtering is necessary.


1 Bridge Stair-Step

1 Bridge PWM fs = 10 x fi

4 Bridge Stair-Step

4 Bridge PWM fs = 10 x fi

Switchmode Noise and Distortion

Instruments Inc. PWM Amplifiers are full bridge output circuits that achieve a high degree of cancellation of the switching frequency harmonic sidebands. The harmonic sidebands (ripple) consist of odd harmonics of the input signal (fi) centered around even harmonics of the switching frequency (fs).

At full output (100% sinewave modulation), single bridge unfiltered ripple includes:

2fs +/- 3fi @ -14dB   The amplitude
4fs +/- 5fi @ -20dB   reference is the
8fs +/- 11fi @ -26dB   fi output signal.
16fs +/- 23fi @ -35dB    

When two bridges are modulated with phase shifted switching frequencies, the 2fs harmonics cancel. Four bridges, such as our model S11-8, will also cancel the 4fs harmonics and so on.

A reasonable output filter is a 2 pole, (Q = 1 with resistive load), low pass cornering at fs/4. This reduces the largest ripple harmonic to -50 dB from a single bridge, -68 dB from a 2 bridge and -86 dB from a 4 bridge amplifier.

As the input frequency is increased above fs/10, the harmonic sidebands spread out and intrude into the signal bandwidth (aliasing). Around fs/4, the output filter can resonate individual sideband harmonics and appear as distortion. Operation between fs/4 and fs/2 (the "Nyquist" limit) is possible if significant distortion is tolerable (10%).

At low modulation, the ripple sidebands reduce both in width and amplitude. The ripple to signal ratio is fairly constant. Voltage feedback reduces the signal band noise floor to about 90 dB below full output. It originates in the PWM comparators. Larger amplifiers average the output of more comparators which results in a greater dynamic range.

Distortion is mainly due to the dead time necessary to prevent simultaneous conduction of the upper and lower switches in each half bridge. At about 30 dB below full output, the modulation is equal to the deadtime, and "crossover" distortion is at a maximum. Voltage feedback may reduce this to about 0.2% It can appear larger if the distortion harmonics resonate with the output filter. Capacitive loads will lower the output filter resonance.

Theoretical Spectrum of Unfiltered Output, Sinewave Input.

100% Modulation fi = 20 kHz, fs = 200 kHz


1 Bridge

2 Bridge

4 Bridge

S11 Series Switching Amplifiers

These amplifiers were originally developed for large systems, however the S16 series is now more appropriate for this. They are based on a half bridge, FET switcher PWB, the OUT-11 which is rated at 1,000 VA.

Instruments Inc. has delivered over 16,000 OUT-11 PWBs since 1987. The reliability of the OUT-11 has been very good. Actual experience has proved greater than a 290,000 hour MTBF per Output PWB.

A pair of boards forms a full bridge. Fast rectifiers and drivers are used for maximum efficiency. Full modulation control is allowed. The transistors are fully protected against load faults, excessive switching frequency, cooling failure, and start-up or power-down transients.

The various models of amplifiers are designated S11-xxm where xx is the number of output boards and m is an optional modifier for special applications. These amplifiers are complete, having a suitable power supply, input preamp and an output filter/transformer system.

Amplifier

Models smaller than the S11-8 are rack mounting, therefore the size and weight is for the amplifier only. The models S11-8 and larger are delivered in a structure (rack), therefore their size and weight is the total and includes the "rack". Multiple cabinets may be designed into a system. We have delivered 3 systems each consisting of 8 S11-64 amplifiers connected to a single load. 

The output transformers in models S11-2 through S11-24 are usually mounted from the front. These transformers may be designed for operation down to 50 Hz, however this reduces the high frequency performance and increases the weight slightly. In addition, models smaller than the S11-32 may be designed as specials to pass through a submarine hatch. The larger models have rear mounted transformers which operate down to 300 Hz and are not designed for submarine use.

Model S11-2A is a 2kVA output stage contained in a chassis consisting of minimal metalwork. It is intended to be mounted in a larger chassis, perhaps with other units for a multi-channel system. This output stage does not have a power supply or output transformer, but does include output filtering.

Model S11-36D and S11-36U are multi-channel amplifiers having 18 separate inputs with 18 separate outputs of 2,200 VA each. The output voltage and current from each channel is monitored during the output burst. Values are stored internally in the PM/FL computer and accessable via a front panel switch and displayed on front panel meters. The last known values are displayed until the next burst. These amplifiers are shock mounted for shipboard use.

Interface

The Interface function is accomplished with an analog Pre-Amp, analog output voltage and current monitors, and digital Fault Detection and Fault Location information. If needed, a summing transformer is included for unusual load matching and/or high voltage output.

Power Supply

In our switching amplifiers, reactive currents are returned to the power supply. Thus, when driving a load with a power factor of 0, either capacitive or inductive, the power drawn from the primary AC source is only 15% of the output VA. Any real power delivered to the load increases the primary AC power. With a resistive load, at full power, the overall efficiency is about 75%.

The power supply may be regulated or unregulated. When a regulated supply is used, the DC voltage will be at the rated voltage for the output PWBs, resulting in the maximum output VA possible. Our regulated supplies have a power factor of 70%.

Our unregulated supplies have the advantage of lower conducted harmonic curents and a power factor of 94-98% at full load. The disadvantage of an unregulated supply is that the maximum rated voltage for the output PWBs is established at high line and no load. At low line and full load, the DC voltage is less, therefore the available output VA of the amplifier is less.



OUT-11 1 kW Half Bridge Switching PWB.

(Click image to enlarge)

Specifications for Standard S11 Series Amplifiers

Type of amplifier Full bridge equivalent, FET output, Switching
Modulation Squarewave, Stair-Step, or PWM
Load power factor range 0 - 100% capacitive or inductive
Distortion (THD) PWM: 2% max, 0.2% typical.
Frequency range (-3 dB) PWM: STD 300 Hz to 20 kHz
or 600 Hz to 40 kHz
PMW: LF 50 Hz to 5 kHz
Stair-Step: max sw freq 160 kHz
RMS noise (PWM only) below max output -60 dB gated on
-120 dB gated off
Current monitor 100 mV/A
Voltage monitor 2 mV/V
Protection No combination of passive loads, input signals or switch settings will cause amplifier failure.
Fault lights Temp limit, voltage limit, current limit, blown fuse
Ambient temperature 0 - 40 degrees C
Primary power (standard) S11-2, 4 208/240 V 60 Hz 1ph
Contact factory for S11-8 - 24 208/240 V 60 Hz 3ph
other AC voltages S11-32 - 64 480 V 60 Hz 3ph

Individual Specifications

Model designation S11-2A S11-2 S11-4 S11-8 S11-16 S11-24
Output watts - continuous 1,000 1,000 2,000 4,000 8,000 12,000
- 100 sec burst @ 20% 2,000 2,000 4,000 8,000 16,000 24,000
Width (inches overall) 6 19 19 24.5 24.5 24.5
Depth (inches overall) 15 22 22 29.5 29.5 29.5
Height (inches overall) 5 7 22.75 49 62 75
Weight, std 10 60 200 600 1,200 1,400
Weight, low freq (pounds) NA NA 275 725 1,500 1,750
Amplifier Photograph S11-2A S11-2 S11-4 S11-8 S11-16 S11-24



Model designation S11-32 S11-36D/U S11-48 S11-56 S11-64
Output watts - continuous 16,000 8 sec on 24,000 28,000 32,000
- 100 sec burst @ 20% 32,000 18 x 2,200 48,000 56,000 64,000
Width (inches overall) 24.5 23.6 24.5 24.5 24.5
Depth (inches overall) 38 25.6 38 38 38
Height (inches overall) 57 67.8 69 75 81
Weight (pounds) 1,600 970 2,000 2,200 2,400
Amplifier Photograph S11-32 S11-36D S11-48 S11-56 S11-64


Models with an "A" have no cabinet, power supply, or output transformer.

Models with a "B" have no power supply.

Some models are available in a Multi Channel configuration. S11-36D or U are 18 channels of 2.2kVA each. Dimensions with shock mounts and stabilizer 26.0 x 27.3 x 75.9 1050 lb.

Contact the factory for special design limitations and cost.


Specifications and prices subject to change without notice.


S16 Series Switching Amplifiers

These amplifiers are intended for large systems. They are based on a half bridge, FET switcher PWB. The OUT-16 has more heatsink and more FET's than the OUT-11 and is rated at higher voltage. A pair of OUT-16 PWBs is rated at 5,000 VA. The OUT-16 circuitry and relative parts stress is virtually the same as the OUT-11. Due to the lower parts count, reduced wiring, and higher power density, the S16 amplifiers are more compact and less expensive per watt than an equivalent S11. Nearly 3 megawatts worth of OUT-16 PWBs have been delivered. 

A pair of boards forms a full bridge. Fast rectifiers and drivers are used for maximum efficiency. Full modulation control is allowed. The transistors are fully protected against load faults, excessive switching frequency, cooling failure, and start-up or power-down transients.

The various models of amplifiers are designated S16-xxm where xx is the number of output boards and m is an optional modifier for special applications. These amplifiers are complete, having a suitable power supply, input preamp and an output filter/transformer system.

Amplifier

The OUT-16 may be configured to be either air cooled or conductive cooled. We have delivered 60 S16-20 amplifiers as air cooled units and several S16-16B amplifiers as water cooled, sealed units for open deck operation.

Interface

The Interface function is accomplished with an analog Pre-Amp, analog output voltage and current monitors, and digital Fault Detection and Fault Location information. If needed, a summing transformer is included for unusual load matching and/or high voltage output.

Power Supply

In our switching amplifiers, reactive currents are returned to the power supply. Thus, when driving a load with a power factor of 0, either capacitive or inductive, the power drawn from the primary AC source is only 15% of the output VA. Any real power delivered to the load increases the primary AC power. With a resistive load, at full power, the overall efficiency is about 75%.

The power supply may be regulated or unregulated. When a regulated supply is used, the DC voltage will be at the rated voltage for the output PWBs, resulting in the maximum output VA possible. Our regulated supplies have a power factor of 70%.

Our unregulated supplies have the advantage of lower conducted harmonic currents and a power factor of 94-98% at full load. The disadvantage of an unregulated supply is that the maximum rated voltage for the output PWBs is established at high line and no load. At low line and full load, the DC voltage is less, therefore the available output VA of the amplifier is less.





OUT-16 2.5 kW Half Bridge Switching PWB.
(Click image to enlarge)


Specifications for Standard S16 Series Amplifiers

Type of amplifier Full bridge equivalent, FET output, Switching
Modulation Squarewave, Stair-Step, or PWM
Load power factor range 0 - 100% capacitive or inductive
Distortion (THD) PWM: 2% max, 0.2% typical
Frequency range (-3 dB) PWM: 300 Hz to 20 kHz
RMS noise (PWM only) below max output -60 dB gated on
-120 dB gated off
Current monitor 100 mV/A
Voltage monitor 2 mV/V
Protection No combination of passive loads, input signals or switch settings will cause amplifier failure.
Fault lights Temp limit, voltage limit, current limit, blown fuse
Ambient temperature 0 - 40 degrees C
Primary power (standard) 480 or 600V 60Hz 3 ph
Contact factory for other voltages


Individual Specifications

Model S16-16L S16-16B S16-20 S16-32B S16-32
Quantity of Chanels 4 4 1 1 8
Output ea channel - W cw 4,000 4,000 19,000 40,000 3,000
Output ea channel - W burst 8,000 13,000 42,400 80,000 7,000
Burst Duration - sec 28 10 100 100 10
Duty cycle 25% 10% 20% 20% 20%
Width (inches overall) 27 21 35 28 35
Depth (inches overall) 32 28 31.5 27 31.5
Height (inches overall) 65 24 35.5 39 54
Weight (pounds) 1,300 400 985 800 1,600
Amplifier Photograph S16-16 S16-16B S16-20 S16-32B S16-32

Units ending with B are DC powered

S16-20 - Stackable in pairs

S16-16B - 4 Channel – External Water Cooled



Other Switching Amplifiers

These compact, switching amplifier PWBs have been designed for high efficiency and versatility and can be adapted to a wide variety of applications. The Output PWBs are either a full bridge or half bridge (usually used in pairs). The outputs are fully protected against open, shorted, or reactive loads of zero power factor.

Some PWBs include a transformer suitable for high frequency applications; most are directly coupled, and require external DC blocking capacitors and an output transformer. Several Output PWBs may be combined for higher output by putting equal voltage transformer secondaries in series. Contact the factory concerning your specific needs.

OUT-18 - This compact board is appropriate for multi channel, high power, low duty cycle applications. Packaged as an S18-26 in a submarine compatible enclosure, it was used in an upgrade to a US Navy sonar system.

OUT-20 - This specialized very narrow PWB is 3 inches wide and includes a preamp and PWM modulator. It operates from a split +-25V supply. It is cooled by making contact to the inside of a pipe.

OUT-26 - The S26-2A module is a 1,500 VA rated assembly and contains an analog pre-amplifier, PWM modulator, 2 output PWBs, and output filter. This module is 7 x 10 x 5 inches without heat sink. This assembly requires external heat sinking. An adequate heat sink for air cooling may be attached to the top of the standard module. The S26-2 is an S26-2A module packaged in an 8.75 inch high rack mounting enclosure and is delivered ready to use, including the DC supply and output transformer.

OUT-27 - This narrow PWB is 3.5 inches wide and includes a preamp and PWM modulator. It operates from a 48V supply. It is cooled by making contact to one edge.

OUT-38 - This 1,000 VA amplifier is just 6 x 15 inches and includes an analog Preamp, PWM modulator, four quadrant bridge amplifier, some output filtering, and an A/B switch to redirect the output to two different loads. It is conductively cooled with an expanding card-lock along one 15 inch edge. This unit is especially suitable for under water applications utilizing conductive cooling to the enclosure.

OUT-40 - This 1,500 VA amplifier PWB is 4.5 x 14 inches and includes an analog Preamp, PWM modulator, four quadrant bridge amplifier, and an output filter. A special 2 channel chassis has been developed which has a small power supply for operation from a standard 115V outlet and 2 OUT-40 PWBs. Click here to see the S40-2


General Specifications of Switching Amplifiers

Load power factor range 0 - 100% capacitive or inductive
Protection No combination of passive loads or input signals, including
overdrive, short or open will cause amplifier failure.
Ambient temperature 0 - 40 degrees C
PWM units only
Distortion (THD) below 20 kHz: 2% max, 0.2% typical
RMS noise (re max output) -60 dB gated on -120 dB gated off
Input impedance (analog) 5 k ohm
Input voltage for full output 1 V RMS for full output


Individual PWB Specifications

Model OUT-18 OUT-20 OUT-26 OUT-27 OUT-38 OUT-40
Output VA 2,500 600 750 600 1,000 1,500
Max duty cycle 1% 100% 100% 100% 20% 100%
Bridge configuration Full Full Half Full Full Full
Heat sinking none Clamp Clamp Clamp Clamp Air
Max frequency kHz 50 PWM 85 PWM 260 85 PWM 85 PWM 85 PWM
Input signal Analog 1VRMS Analog 2VRMS Digital TTL Analog 1VRMS Analog 1VRMS Analog 1VRMS
Connection Method 96 DIN Double Ended Plugs 96 DIN DB-25 Double Ended Plugs 35 EDAC
Width 6.0 2.8 4.5 3.0 6.0 4.5
Length 12.0 15.7 8.3 15.75 13.0 14.0
Thickness 2.5 0.6 1.2 1.0 0.8 1.3
Main DC Supply needed 250 -25 +25 48-59 48-59 250 350
Aux Dc supply needed -15,+15 None +12 +12 -15,+15 +15
Amplifier Photograph OUT-18 OUT-20 OUT-26 OUT-27 OUT-38 OUT-40

All units rated at 100% duty must have adequate heat sinking. Be advised that connection to these PWBs and external wiring may affect performance. These high performance PWBs require knowledgeable connections to work properly. Consulting services are available.


Wired and Tested Amplifier Assemblies

Model S18-26 S26-2A S26-2
18 Channels Module Rack Mount
Input power needed 440 V 3ph 48-59 VDC 115*/230 VAC
Input Signal Analog Analog Analog
Frequency Range (-3 dB) 10-35 kHz 50 Hz - 30 kHz 50 Hz - 30 kHz
Modulation PWM PWM PWM
Output VA 2,500 VA/chan 1,500 1,500
Output Watts 10 mSec 1,500 1,200
Max duty cycle 1% 100% 100%
Size (inches) 18 x18x 60 7 x 10 x 5 8.75 high
Weight (pounds) 700 15 65
Amplifier Photograph S18-26 S26-2A S26-2

* If the S26-2 is operated on 115V, the max CW power out is only 900W. For heat sink on S26-2A module, add 3 lbs, and 1.6 in. to the 5 in. dimension. For output transformer cost, size, and weight, contact factory. Specifications and prices subject to change without notice.

L Series Linear Amplifiers

Each of our L series amplifiers contains regulated power supplies, a Pre-Amplifier PWB, Output PWBs, and an output transformer system. The L series Output PWB is a current source. Up to 50 PWBs may be combined and still maintain proper sharing of current. This is the configuration of an L50, our largest L series amplifier. Voltage feedback is used to create a voltage source or resistive source.

These amplifiers, together with the M series, are dual rated. That is, they are capable of both continuous as well as burst output. During continuous output into a reactive load, the heat sinks warm up. The heat sink temperature is sensed by the Pre-Amplifier and used to determine a safe current limit. While driving short tone bursts, or resistive loads, the heat sinks are cooler, therefore the current limit is increased by as much as 2.5 times. This function is automatic and on-going, cycle by cycle. This enables the amplifier to safely maximize output power under all conditions.

The enhanced power output during a 1 second tone burst is obtained by a slow average current limit in the power supply. The system is well protected, and there is no combination of input signal and passive loads which will damage these amplifiers. Active loads must be less powerful than the amplifier rating.

Models L2, L6, and L10 are standard rack mount units. They require only a single phase main power source. The larger models (L20 - L50) are all powered from a three phase line. Voltage should be specified as "Line to Line".

In order to optimize the high frequency performance and to fit in a small chassis, the L2 output transformer is only large enough for full power operation down to 500 Hz. The high end is limited mostly by the slewing rate of the output transistors. This gives usable continuous rated performance up to 150 kHz (-3 dB).

The L6 has an output transformer capable of -3 dB continuous rated performance from 40 Hz to 120 kHz.

In models L20 and larger, each bank of 10 Output PWBs is wired independently to its own output transformer. This has enabled us to obtain the same superior high frequency performance from an L50 as we can achieve from an L10.

The output transformers have multiple secondaries with taps to match various loads. These secondaries are put in series and parallel combinations. This is done with relays which are always "cold switched" since the relays are commanded to move only after the amplifier has been automatically inhibited. The various load impedance taps may be selected by a front panel switch or controlled remotely. At least 70% of the secondary copper is used at all times.

Selectable Source Impedance

Our L series amplifiers have a switch to select the characteristic of the source impedance. As a voltage source, the output voltage tends to remain constant as the load impedance varies. As a current source, the current does the same. As a resistive source, the amplifier appears to have a resistor in series with the output of a voltage source. Full power is still available for the load. The value of this synthesized resistor is approximately the same as the matching burst-rated load impedance. The resistive source has the advantage of damping out ringing and other transients. Transducer calibration in small tanks is an ideal application of the resistive source.

Linear, Low Distortion

Our L series amplifiers are very linear, even without feedback. In the current source mode (open loop), midband distortion is typically 1.0%. Voltage feedback reduces this to less than 0.1%. The dynamic range of more than 100 dB makes them useful for a wide variety of applications.

Low Frequency Option

On Models L10-L50 the low frequency performance may be specified to -3 dB at 50 Hz, rather than the standard 200 Hz. This option requires that we build a larger output transformer system. This may extend delivery to 4 months, depending on delivery of core materials and it will lower the high frequency limit (-3dB) to about 60 kHz when operating at the CW power level and about 30 kHz when at the Burst level. The amplifier size and price is unchanged, but its weight increases slightly. This option is not available on the L2 due to size constraints. Our standard model L6 has an output transformer with a -3 dB operating bandwidth at the CW power level of 40 Hz to 120 kHz.



Specifications For Standard L Series Amplifiers

Type of amplifier Class A Linear Voltage, Current or Resistive Source
Load power factor range 0 - 100% capacitive or inductive
Distortion (THD) Voltage Source 2% or less over full frequency range, typically 0.1% midband
Input impedance 5K Ohm minimum
Input voltage for full output 1 V RMS nominal, 3 V RMS at highest frequency
Gate signal TTL levels (5 V)
Selection of Output Voltage Tap Relays operated by front panel switch or remote control
Output Voltage Taps L2 88, 132, 175, 220, 265
(V RMS) L6, L10, L20 106, 150, 212, 300, 424, 600, 848, 1200
L30, L40, L50 212, 300, 424, 600, 848, 1200
Frequency Range
-3 dB from the continuous mode power level, Burst level power will have a lower high freq limit
L2 400 Hz to 150 kHz
L6 40 Hz to 120 kHz
L10 - L50 200 Hz to 120 kHz
LF option 50 Hz to 60 kHz
RMS noise (1-100 kHz) re full output -80 dB max gated ON, -120 dB max gated OFF
Voltage Monitor 10 mV/V
Current Monitor 100 mV/A
Protection No combination of loads, signals or switch settings will cause amplifier failure
Fault lights Over-temp, over current, blown fuse
Ambient temperature 0 - 40 degrees C
Primary power L2 120/208/240 Volts 50/60 Hz 1 phase
L6 208/240 Volts 50/60 Hz 1 phase
L10 208/240 Volts 60 Hz 1 phase
L20 - L50 208/240 Volts 60 Hz 3 phase




Model Designations L2 L6 L10 L20 L30 L40 L50
Output VA - continuous 260 800 1,300 2,600 4,000 5,200 6,500
1 sec burst @ 10% 650 2,000 3,300 6,500 10,000 13,000 16,500
Depth (inches) 18 18 18 35 35 35 35
Height (inches overall) 5.25 14.00 26.25 52.00 80.00 80.00 80.00
Weight (pounds) 52 165 240 600 825 1,000 1,200
Amplifier Photograph L2 L6 L10 L20 L30 L40 L50
Other Photographs L Series Output PWB
Special L2 Special L6

The height of L20 - L50 is overall in a rack which has extra space for a VIT-13 or other instrument.

M Series Linear Amplifiers

Our M series amplifiers are the result of a three year research and development program to create a reliable source of linear power beyond the high frequency limits of our L series amplifiers.

Each Output PWB drives an individual output transformer which is located on the board to minimize wiring inductance. The small size of this transformer and second breakdown considerations of the output transistors limit the low frequency response to 10 kHz.

In order to maintain full control of the very fast output transistors used, each output transistor has its own high speed driver located very close to the transistor. The M series is available only as a voltage source.

Each amplifier board is rated at 100 VA continuously or 250 VA in tone bursts up to 1 second duration and 10% duty. As with our L series, these ratings are into any power factor load. The standard models M2, M4, and M8 contain 2, 4, and 8 Output boards respectively. The M4 is actually an M8 with 4 Output PWBs removed and may be upgraded at any time.

The high frequency response with resistive or inductive loads is about 500 kHz. With slightly capacitive loads, these amplifiers work up to 1 MHz.

As with all our amplifiers, the load on these amplifiers may be shorted, opened, or reactive with any magnitude and phase angle with no damage occurring to the amplifier.


Specifications For Standard M Series Amplifiers

Type of amplifier Class AB Linear Voltage source
Load power factor range 0 - 100% capacitive or inductive
Distortion (THD) 2% or less over full freq range Typically 0.25% midband
Input impedance 5 k ohm minimum
Input voltage for full output 1 V RMS nominal, 3 V RMS at highest frequency
Gate signal TTL levels (5 V)
Selection of Output Voltage Tap Relays operated by front panel switch or remote control
Output Voltage Taps (V RMS) M2 60, 85, 120, 175
M4 60, 85, 120, 175, 245, 345
M8 60, 85, 120, 175, 245, 345, 490, 690
Frequency range (-3 dB) 10 kHz to 500 kHz
RMS noise (10-500 kHz) ref full output -80 dB max gated ON, -120 dB max gated OFF
Current monitor 100 mV/A
Voltage monitor 10 mV/V
Protection No combination of loads, signals or
switch settings will cause amplifier failure
Fault lights Over-temp, over current, blown fuse
Ambient temperature 0 - 40 degrees C
Primary power M2 120/208/240 V 50/60 Hz 1 ph
M4 - M8 208/240 V 50/60 Hz 1 ph



 
Model designation M2 M4 M8
Output VA - continuous200 400 800
- 1 sec burst @ 10 % 500 1,000 2,000
Depth (inches) 18 24 24
Height (inches) 5.25 19.25 19.25
Weight (pounds) 50 160 170
Amplifier Photograph M2 M4 M8
Output Amplifier Photograph M Series Output PCB

VIT Voltage / Current Sensor

Accurate high frequency measurements of high voltages and currents are difficult. The limited input range of instrumentation, such as A/D converters, is often incompatible with a wide dynamic range. Driving balanced or floating loads complicates the issue further. It is very important to sense both voltage and current at the same point in order to get accurate phase information. Our VIT is inserted between the output of the power amplifier and the load.

This instrument is electrically equivalent to a wide band potential transformer and a shielded current transformer. It can tolerate 1000 V of common mode voltage up to 200 kHz, while maintaining the specified accuracies of magnitude and phase.

The outputs of the voltage and current channels are single ended and have a 50 ohm source resistance. These analog monitor voltages have the same waveform as the voltage and current under test. Their magnitudes are accurately proportional to the original magnitudes, and the phase shifts between the voltage and current channels are matched. Phase information will remain valid if the low level output cables are matched in length, termination, and characteristics. These monitor signals are available at an MS type connector on the rear, as well as at BNCs on the front panel.

VIT-10

This is a single range version which uses differential voltage sense and average current sense. It produces a buffered, single ended low level output of 1 mV/V and 100 mV/A. It is limited to 2,500V. All other specs are the same as the VIT-13. A VIT-10M-6 is a 3U (5.25 inch) high rack mounting chassis which contains 6 channels. Units with fewer channels are available.

VIT-13

This instrument has four levels of sensitivity of voltage and current which may be selected locally or via isolated TTL logic. In addition, it has a current transformer in both the high and low leg which may be selected by a front panel switch.



Specifications For VIT-13


Voltage Sensitivity 100 uV/V, 1 mV/V, 10 mV/V, 100 mV/V
Current Sensitivity 10 mV/A, 100 mV/A, 1 V/A, 10 V/A
Maximum input 5 kV RMS, 10 kV peak, 30 A RMS, 100 A peak
Maximum output 10 V peak (7 V RMS for sine waves) 100 mA
Output impedance 50 ohms
Accuracy:
100 Hz-50 kHz 1% of reading + 0.1% of full scale 1 deg of phase
40 Hz-200 kHz 2% of reading + 0.2% of full scale 2 deg of phase
10 Hz-500 kHz 5% of reading + 0.2% of full scale 5 deg of phase
Common mode rejection 34 dB from 100 Hz to 100 kHz
24 dB from 10 Hz to 200 kHz
Primary Power 120/240 V 50/60 Hz 1 ph
Size (inches) 5.25 high Rack Mounting
Weight (pounds) 18
Photograph VIT-10M-6 VIT-13



Typical Amplitude Accuracy vs. Frequency

Specifications and prices subject to change without notice.

Switching Amps
Switching Info
S11
S16
Other Switchers
Linear Amplifiers
L Series
M Series
Test Equipment
VIT Voltage / Current Sensor