Model 440 User`s Guide

Model 440 User`s Guide
Operating Instructions
Brownlee Precision Model 440
Four-Channel Amplifier and Signal Conditioner
The Model 440‟s power requirements are 120 VAC, 47-63 Hz
unless otherwise indicated on the back panel near the power
connector. Run an IEC line cord from a wall socket to the back
panel power connector. The 2 Amp, 5x 20 mm type fuse is located
in the back panel power connector.
Turn on the power using the front panel power switch. The “ON”
will illuminate and, after a pause, the LED alphanumeric displays
will spell the startup message. After another pause, the displays
will spell out the amplifier settings and the amplifier is ready for
Troubleshooting: If the “ON” indicator does not light up, check
the fuse and power connection. If the “ON” does light up, but the
alphanumeric displays do not spell the startup message or
amplifier settings, push the reset button on the front panel.
Signal Connections:
Each of the four channels is an independent voltage amplifier with
a non-inverting (A) input, an inverting (B) input and an output, all
with BNC connectors. The input and output voltage ranges are +/10 Volts. Each output is capable of driving +/- 100 mA.
Amplifier Settings:
There are 5 main parameters, which can be adjusted on each
amplifier channel: Gain, Lowpass Filter cutoff frequency,
Highpass Filter cutoff frequency, Output Offset voltage, and Input
Selection. There is a button corresponding to each one of these
parameters. Pushing one of these buttons puts that parameter‟s
value on the 8-digit alphanumeric display. The knob can be used to
adjust that parameter.
To set the gain, for example, push the „Gain‟ button and then turn
the knob until the desired value is displayed.
To completely configure a channel of the amplifier, all 5
parameters must be set using the buttons and the knob. The
parameters may be set in any order.
It is important to remember that pushing a parameter button once
does not change the amplifier settings; it simply changes the
alphanumeric display. Turning the knob is the way to change the
amplifier‟s internal settings.
The amplifier‟s output is not affected by which parameter happens
to be displayed. You may want to leave the most frequently
adjusted parameter on the display. The amplifier will retain all the
settings for each channel when power is turned off, even if the unit
is unplugged.
To set the amplifier‟s gain, push the „Gain‟ button and turn the
knob until desired gain is displayed. The gain ranges from 0.1 to
10,000. Gains of 1000 to 10,000 are abbreviated 1 K to 10 K, etc.
The gain can be displayed either as a ratio or in decibels:
, for example. See “Setups” section
for an explanation of switching between these two modes.
Lowpass Filter
To set the Lowpass filter‟s cutoff frequency, push the „Lowpass
Filter‟ button and turn the knob until desired value is displayed.
The cutoff frequency ranges from 20 Hz to 50 kHz. There is also a
wideband setting, (
) with a cutoff frequency of
approximately 300 kHz.
The filter characteristic is an 8 pole Bessel function for all values
from 20 Hz to 50 kHz. If your amplifier has a custom
configuration differing from this, it will be noted on the last page
of this manual.
Highpass Filter (Input Coupling)
To set the Highpass Filter cutoff frequency, push the „Highpass
Filter‟ button and turn the knob until the desired value is displayed.
The cutoff frequency of the single-pole Highpass filter can be
varied from 0.01 Hz to 1 kHz.
In addition, the inputs can be true-DC-coupled (
) or DCcoupled with Autozero capability (
). See Autozero
section for an explanation of this feature.
The Highpass Filter is useful when you need to amplify a small
signal whose average voltage (or DC level) is not at 0 Volts, or
worse yet, may be slowly drifting relative to ground.
If the Gain is  100 the Highpass Filter can remove DC input
offset voltages up to +/- 10 Volts. If the Gain > 100, the Highpass
Filter can remove DC input offset voltages up to +/- 100 mV. If
you need both Gain > 100 AND common mode voltage > +/- 100
mV, you will need to cascade two channels. The first channel
should have G < 100 and the Highpass filter ON; the second
channel should perform the additional amplification.
Output Offset
To set the output offset voltage, push the „Output Offset‟ button
and turn the knob until the desired value is displayed. Output offset
is abbreviated “OS”. The offset voltage may be varied from – 10
Volts to + 10 Volts.
Handy tip: pushing the Output Offset button twice will immediately
reset the output offset voltage to zero.
Input Select
To select which input is to be amplified, push the „Input Select‟
button and turn the knob until desired configuration is displayed.
“Gnd” ignores both input lines and internally ties the inputs to 0
Volts for equipment setup and testing.
The “A” setting amplifies the single-ended signal on the A input.
The “-B” setting amplifies and inverts the single-ended signal on
the –B input. The “A-B” setting amplifies the difference between
the A and –B inputs.
Handy tip: Once the input Select button has been pushed, your
input choice may be made by either turning the knob, or by
repeatedly pushing the Input Select button. For example, the first
time you push Input Select, the present input setting is written to
the alphanumeric display without changing it. Each additional
push of the button, however, will advance the amplifier through its
four options: Gnd, A, -B, A-B.
Special Functions of the Model 440:
Line Notch Filter
Pushing this button toggles the notch filter on and off. When on,
this filter removes sinusoidal interferences at the line frequency. It
is factory set for 50 Hz or 60 Hz.
Notch filters will distort square waves of frequencies lower than
the center frequency of the notch. For this reason, you should
generally keep the notch filter OFF, and only use it when line
noise is excessive.
If the Highpass Filter is set to any value except
, then
pushing the “Autozero” button resets the centerline level of the
output to 0 Volts (plus or minus the Output Offset setting).
Pushing Autozero turns off the output for approximately one
Digital Voltmeter
Pushing the DVM button on the channel 1 or 2 will put the DC
level of the output on the alphanumeric display. The displayed
value is post-gain and post-filtering.
To read the DC level of the input, you must first set:
Gain = 1
Highpass Filter = DC
Output Offset = 0 Volts
Turning on the DVM does not affect the amplifier settings or the
output signal.
There are two modes for the amplifier memory: Single Memory
Mode is easy to use, and Multiple Memory Mode offers more
memory options. See “Setups” section for instructions on how to
switch between these two modes.
Single Memory Mode: Pushing the “Memory STO” button saves
this channel‟s settings to this channel‟s memory. Pushing the
“Memory RCL” button reconfigures this channel to the settings in
this channel‟s memory.
ALL six amplifier settings are stored to memory, and all six
recalled from memory: Gain, Lowpass Filter, Highpass Filter,
Output Offset, Input Select, and Line Notch Filter.
Multiple Memory Mode: In this mode, there is a choice of 8
memory locations for each channel. Four of these locations are
unique to the channel. They are numbered 10, 11, 12, and 13 on
channel one; 20, 21, 22, 23, on channel two, etc. In addition, there
are 4 memory locations which are common to all channels. These
are designated A, B, C, and D.
In Multiple Memory Mode, storing the current settings to memory
is done in three steps:
1. Push the memory STO button. The display will show:
, for example.
2. Turn the knob until the desired memory location is
, for example.
3. Push the Memory STO button a second time to confirm.
The display will briefly show:
In Multiple Memory Mode, recalling the settings from memory is
done the same way:
1. Push the Memory RCL button.
The display will show:
, for example.
2. Turn the knob until the desired memory location is
, for example.
3. Push the Memory RCL button a second time to confirm.
The display will briefly show:
If you wish to cancel the memory command after step 1 or 2,
simply stop and wait 3 seconds, the memory command will time
out without executing anything.
The common memory locations, A, B, C, and D are useful to
transfer settings from one channel to another. For example, to
make channel 4‟s setting identical to channel 3‟s, follow these
On channel 3, store to location B
On channel 4, recall from location B
(Location A, C, or D could also have been used.)
You may switch between single-memory and multiple-memory
modes without losing the data in memory. In single-memory
mode, you are actually using memory location 10 on channel one,
location 20 on channel two, etc.
Pushing the “Setups” button puts certain amplifier setup choices
on the alphanumeric displays. Turn the knob beneath the display to
change its setting. Push the “Setups” button a second time to exit
this mode. Under Setups:
LED: changes the brightness of the LED displays
MEM: switches between single-memory and multiple-memory
determines whether Gain is displayed as a ratio or in dB.
Gain (dB) = 20 log10 Gain (ratio)
When an amplifier parameter is adjusted using the knob, the values
can be made to change in small incremental steps (FINE mode) or
take larger jumps to the next “round” value (COARSE mode).
Changing Coarse/Fine only affects future adjustments; the current
settings do not get “rounded-off”.
Input Resistance Switch
There is a small slide switch between the A and B input
connectors. Its settings are as follows:
General Purpose: The input resistance of the amplifier is 1 M.
This is the recommended position for most users.
High Impedance: The input resistance of the amplifier is 1010 .
This may be useful when high resistance probes are used as the
Low Noise: This input resistance of the amplifier is 100 K and
the input bias current is typically 3 A. At Gains > 100, the noise
is slightly reduced with this setting.
The electronic components at each stage of the amplifier have
inherent offset voltages, which could cause a shift of the “zero”
level of the output. The Brownlee Precision Model 440 has a selftrimming feature, which compensates for these errors
Every time an amplifier parameter is changed, the amplifier goes
through a quick self-calibration routine. During this routine the
output will be invalid for approximately 25–100 mS, depending on
the Lowpass and Highpass filter settings.
The Self-trimming routine is only performed on the channel whose
gain is being changed. The other three channels are unaffected.
If you notice the zero level of the output has drifted (as may be
seen in the first few minutes after the amplifier is turned on) you
can invoke the self-trimming feature by changing a parameter, or
by pushing Autozero.
ALWAYS remove the line cord before opening the cover of the
Although they are unlikely to ever need adjustment, there are two
trimpots on each channel. One is for adjusting Gain and the other
is for adjusting the center frequency of the line notch filter. The
trimpots are labeled.
Lithium Rechargeable Battery: Very unlikely this battery will lose
its charge. If the amplifier is no longer holding its settings when
power is turned off, or you find you must frequently push the reset
button to turn the amplifier on, then contact Brownlee Precision
Company for replacement instructions.
Amplifier Specifications:
Gain Range
Gain Accuracy
0.1 to 10,000
< 2% error
Input Impedance, Gen. Purp. Mode
Input Impedance, Low Noise Mode
Input Impedance, High Imp. Mode
Input Voltage Range, G ≤ 100
Input Voltage Range, G > 100
Input Bias Current, Gen. Purp. Mode
Input Bias Current, Low Noise Mode
Input Offset Voltage
Output Offset Voltage
Common Mode Rejection Ratio
Slew Rate (input and output)
Lowpass filter characteristic
1 M, 15 pF
100 K, 15 pF
1010 , 15 pF
+/- 10 Volts
+/- 100 mV
< 50 pA
< 12 µA
< 5 µV
< 15 mV
> 70 dB
10 V/µS
8 poles Bessel
Wideband Voltage Noise, ref. to input
Wideband Voltage Noise, ref. to output
Noise Spectrum. 1 kHz, ref. to input
< 20 µVp-p
< 15 mVp-p
10-nV/ √Hz
At low gains, the total output noise is approximately RTO noise. At high gains, the total output noise
is approximately Gain x RTO noise.
Output Voltage Range
Output Current
Output Offset Control Range
+/- 10 Volts
+/- 100 mA
+/- 10 Volts
Cross-talk Rejections *
No load on transmitting channel
130 dB
100  load on transmitting channel 120 dB
* Low impedance signal or ground on receiving channel
These specifications are believed to be accurate as of 2012, but are subject to change without notice.
Warning: This instrument is not for use on human subjects.
Model number:
Serial number:
Firmware version:
V 3.6
Custom Options:
Ship Date:
12 months, parts and labor
Instruction manual:
440 Rev. H April, 2014
Contact Information:
NeuroPhase, LLC
2318C Walsh Ave
Santa Clara, CA 95051
1-408-538-3101 Fax
Brownlee Precision is a division of NeuroPhase LLC
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