NPI VA-10M User manual

OPERATING INSTRUCTIONS AND
SYSTEM DESCRIPTION OF THE
VA-10M
VOLTAMMETRIC AND
AMPEROMETRIC AMPLIFIER
FOR EPMS SYSTEMS
VERSION 4.2
npi 2017
npi electronic GmbH, Bauhofring 16, D-71732 Tamm, Germany
Phone [phone]; Fax: [phone]
[email protected]; http://www.npielectronic.com

VA-10M User Manual
version 4.2 page 2
Table of Contents
1. Safety Regulations ............................................................................................................ 3
2. EPMS-07 Modular Plug-In System .................................................................................. 4
2.1. General System Description / Operation ..................................................................... 4
2.2. EPMS-07 Housing ....................................................................................................... 4
2.3. EPMS-H-07 Housing ................................................................................................... 4
2.4. EPMS-E-07 Housing ................................................................................................... 4
2.5. EPMS-03 ..................................................................................................................... 5
2.6. PWR-03D .................................................................................................................... 5
2.7. System Grounding ....................................................................................................... 6
EPMS-07/EPMS-03 .................................................................................................... 6
EPMS-E-07 .................................................................................................................. 6
2.8. Technical Data ............................................................................................................. 6
EPMS-07, EPMS-E-07 and EPMS-H-07 .................................................................... 6
EPMS-07 and EPMS-H-07 .......................................................................................... 6
EPMS-E-07 .................................................................................................................. 6
EPMS-03 ..................................................................................................................... 6
3. Introduction ...................................................................................................................... 7
4. VA-10M Components ...................................................................................................... 8
5. VA-10M System ............................................................................................................... 8
5.1. System Description ...................................................................................................... 8
5.2. Description of the Front Panel ..................................................................................... 9
6. Headstage ......................................................................................................................... 12
6.1. Headstage Elements ..................................................................................................... 12
7. Operation .......................................................................................................................... 13
7.1. Setting up the VA-10M ............................................................................................... 13
7.2. Testing Basic Functions of the VA-10M ..................................................................... 14
Open Circuit Test ........................................................................................................ 14
DC Accuracy ............................................................................................................... 14
Dynamic Test / Frequency Response .......................................................................... 15
7.3. Carbon-Fiber Electrodes .............................................................................................. 16
7.4. Reference- / Counterelectrode ..................................................................................... 16
7.5. Amperometric Measurements ..................................................................................... 16
7.6. Cyclic Voltammetry .................................................................................................... 16
8. Literature .......................................................................................................................... 17
9. Technical Data .................................................................................................................. 21
10. VA-10M with 3-Electrode Headstage .............................................................................. 22

VA-10M User Manual
version 4.2 page 3
1. Safety Regulations
VERY IMPORTANT: Instruments and components supplied by npi electronic are NOT
intended for clinical use or medical purposes (e.g. for diagnosis or treatment of humans),
or for any other life-supporting system. npi electronic disclaims any warranties for such
purpose. Equipment supplied by npi electronic must be operated only by selected, trained
and adequately instructed personnel. For details please consult the GENERAL TERMS
OF DELIVERY AND CONDITIONS OF BUSINESS of npi electronic, D-71732 Tamm,
Germany.
1) GENERAL: This system is designed for use in scientific laboratories and must be operated
by trained staff only. General safety regulations for operating electrical devices are to be
followed.
2) AC MAINS CONNECTION: While working with the npi systems, always adhere to the
appropriate safety measures for handling electronic devices. Before using any device
please read manuals and instructions carefully.
The device is to be operated only at 115/230 Volt 60/50 Hz AC. Please check for
appropriate line voltage before connecting any system to mains.
Always use a three-wire line cord and a mains power-plug with a protection contact
connected to ground (protective earth).
Before opening the cabinet unplug the instrument.
Unplug the instrument when replacing the fuse or changing line voltage. Replace fuse only
with an appropriate specified type.
3) STATIC ELECTRICITY: Electronic equipment is sensitive to static discharges. Some
devices such as sensor inputs are equipped with very sensitive FET amplifiers, which can
be damaged by electrostatic charge and must therefore be handled with care. Electrostatic
discharge can be avoided by touching a grounded metal surface when changing or
adjusting sensors. Always turn power off when adding or removing modules,
connecting or disconnecting sensors, headstages or other components from the
instrument or 19” cabinet.
4) TEMPERATURE DRIFT / WARM-UP TIME: All analog electronic systems are sensitive
to temperature changes. Therefore, all electronic instruments containing analog circuits
should be used only in a warmed-up condition (i.e. after internal temperature has reached
steady-state values). In most cases a warm-up period of 20-30 minutes is sufficient.
5) HANDLING: Please protect the device from moisture, heat, radiation and corrosive
chemicals.

VA-10M User Manual
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2. EPMS-07 Modular Plug-In System
2.1.General System Description / Operation
The npi EPMS-07 is a modular system for processing of bioelectrical signals in
electrophysiology. The system is housed in a 19” rackmount cabinet (3U) has room for up to 7
plug-in units. The plug-in units are connected to power by a bus at the rear panel.
The plug-in units must be kept in position by four screws (M 2,5 x 10). The screws are important
not only for mechanical stability but also for proper electrical connection to the system housing.
Free area must be protected with covers.
2.2.EPMS-07 Housing
The following items are shipped with the EPMS-07 housing:
 EPMS-07 cabinet with built-in power supply
 Mains cord
 Fuse 2 A / 1 A, slow (inserted)
 Front covers
Figure 1: Left: front view of empty EPMS-07 housing.
In order to avoid induction of electromagnetic noise the power supply unit, the power switch
and the fuse are located at the rear of the housing (see Figure 2, right).
2.3.EPMS-H-07 Housing
In addition to the standard power supply of the EPMS-07, the EPMS-H-07 has a built-in high
voltage power supply. This is necessary for all MVCS / MVCC modules, the HVA-100, HV-
TR150 and HVC-03M modules. The output voltage depends on the modules in use.
2.4.EPMS-E-07 Housing
The following items are shipped with the EPMS-E-07 housing:
 EPMS-E-07 cabinet
 External Power supply PWR-03D
 Power cord (PWR-03D to EPMS-E-07)
 Mains chord
 Fuse 1.6 A / 0.8 A, slow (inserted)
 Front covers
The EPMS-E-07 housing is designed for low-noise operation, especially for extracellular and
multi channel amplifiers with plugged in filters. It operates with an external power supply to
minimize distortions of the signals caused by the power supply.

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2.5.EPMS-03
The following items are shipped with the EPMS-07 housing:
 EPMS-07 cabinet with built-in power supply
 Mains cord
 Fuse 0,4 A / 0,2 A, slow (inserted)
 Front covers
Figure 2: Left: front view of EPMS-03 housing. Right: rear panel detail of EPMS-03 and
EPMS-07 housing.
In order to avoid induction of electromagnetic noise the power supply unit, the power switch
and the fuse are located at the rear of the housing (see Figure 2, right).
2.6.PWR-03D
The external power supply PWR-03D is capable of driving up to 3 EPMS-E housings. Each
housing is connected by a 6-pole cable from one of three connectors on the front panel of the
PWR-03D to the rear panel of the respective EPMS-E housing. (see Figure 3, Figure 4). A
POWER LED indicates that the PWR-03D is powered on (see Figure 3, left). Power switch,
voltage selector and fuse are located at the rear panel (see Figure 3, right).
Note: The chassis of the PWR-03D is connected to protective earth, and it provides protective
earth to the EPMS-E housing if connected.
Figure 3: Left: PWR-03D front panel view Right: PWR-03D rear panel view.
Note: This power supply is intended to be used with npi EPMS-E systems only.

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version 4.2 page 6
2.7.System Grounding
EPMS-07/EPMS-03
The 19" cabinet is grounded by the power cable through the ground pin of the mains connector
(= protective earth). In order to avoid ground loops the internal ground is isolated from the
protective earth. The internal ground is used on the BNC connectors or GROUND plugs of the
modules that are inserted into the EPMS-07 housing. The internal ground and mains ground (=
protective earth) can be connected by a wire using the ground plugs on the rear panel of the
instrument. It is not possible to predict whether measurements will be less or more noisy with
the internal ground and mains ground connected. We recommend that you try both
arrangements to determine the best configuration.
EPMS-E-07
The 19" cabinet is connected to the CHASSIS connector at the rear panel. It
can be connected to the SYSTEM GROUND (SIGNAL GROUND) on the
rear panel of the instrument (see Figure 4).
The chassis can be linked to PROTECTIVE EARTH by connecting it to the
PWR-03D with the supplied 6-pole cable and by interconnecting the
GROUND and PROTECTIVE EARTH connectors on the rear panel of the
PWR-03D (see Figure 3). Best performance is generally achieved without
connection of the chassis to protective earth.
Important: Always adhere to the appropriate safety measures.
Figure 4: Rear panel connectors of the EPMS-E-07
2.8.Technical Data
EPMS-07, EPMS-E-07 and EPMS-H-07
19” rackmount cabinet, for up to 7 plug-in units
Dimensions: 3U high (1U=1 3/4” = 44.45 mm), 254 mm deep
EPMS-07 and EPMS-H-07
Power supply: 115/230 V AC, 60/50 Hz, fuse 2 A / 1 A slow, 45-60 W
EPMS-E-07
External power supply (PWR-03D) 115/230 V AC, 60/50 Hz, fuse 1.6/0.8 A, slow
Dimensions of external power supply: (W x D x H) 247 mm x 180 mm x 90 mm
EPMS-03
Power supply: 115/230 V AC, 60/50 Hz, fuse 0.4 A / 0.2 A slow
Maximum current supply: 500 mA
Dimensions: 3U high (1U=1 3/4” = 44.45 mm), 245 mm deep, 265 mm wide

VA-10M User Manual
version 4.2 page 7
3. Introduction
Recently, electrochemical methods using carbon-fiber microelectrodes have been applied to
measure the release of oxidizable transmitter from single cells, and, even more impressively,
from single exocytotic vesicles. Transmitters that are oxidizable and which, therefore, can be
measured with this approach, include serotonin, dopamine, adrenaline, and noradrenaline. In
addition, some peptides or proteins such as insulin may be oxidizable owing to the presence of
oxidizable amino acids such as cysteine or tyrosine.
Cells that have been studied successfully with this technique include adrenal chromaffin cells,
sympathetic neurons, mast cells, pancreatic beta cells, carotid glomus cells and melanotrophs,
but the list is growing. In addition, in brain slices simultaneous intracellular and voltammetric
studies have been made to correlate intracellular electric signals with transmitter release.
Two useful electrochemical approaches are amperometry and cyclic voltammetry. In
amperometry, a DC potential is applied to a carbon-fiber microelectrode. The applied potential
appears at the interface between the carbon and the mammalian ringer solution. If the potential
is much greater than the redox potential for a given transmitter, then molecules of transmitter
diffusing to the carbon surface are oxidized rapidly yielding a current that can be measured.
The sensitivity of the amperometric approach, in particular, has provided an unprecedented
look at the time course of transmitter release revealing distinct phases of release. On the other
hand, the amperometric approach provides little information about the substance being oxidized
or reduced.
Cyclic voltammetry provides a limited amount of information about the substance being
studied, at some expense to the time resolution. In this approach a cyclically repeating voltage
waveform, typically consisting of voltage ramps, is applied to the carbon-fiber electrode and
the resulting current is plotted as a function of the applied voltage (after subtraction of a
"background" record obtained in the absence of the redox species). Since different substances
have different potentials for oxidation and for reduction one can distinguish transmitters from
each other.
For more detailed informations about the principles of electrochemical measurements at single
cells and the fabrication of carbon-fiber microelectrodes refer to several recent reviews.

VA-10M User Manual
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4. VA-10M Components
The following items are shipped with the VA-10 system:
 VA-10M amplifier
 Headstage
 GND connector for headstage (1 mm)
 User manual
Optional accessories:
 Carbon-fiber electrode holder
 Carbon-fiber electrodes (CFE),  5µm
 Headstage with differential input
 Four VA-10 amplifier system:
Modified EPMS housing, 4 VA-10 amplifier modules, and a four-in-one headstage
5. VA-10M System
5.1.System Description
The VA-10M is a sensitive (picoampere range) current amplifier that is intended for
voltammetric measurements with carbon-fiber microelectrodes in biological systems, where the
total currents do not exceed 20 nA. It can be used for either DC amperometry using the built-
in voltage source or it can be operated with user-supplied external voltage waveforms (e.g. for
cyclic voltammetry).
The VA-10M is ideally suited for measurements with carbon-fiber disk microelectrodes having
diameters of 10 µM or less from single cells plated onto glass cover slips. However, it can also
be used for measurements made on superficially located cells in tissue slices. The VA-10M is
not recommended for use in in vivo recordings with carbon-fiber electrodes having long
cylindrical measuring surfaces, because in this case currents approach the µA range and a third
electrode is required to compensate for the IR drop as currents flow through the extracellular
fluid.

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5.2. Description of the Front Panel
Figure 5: VA-10M front panel view
In the following description of the front panel elements each element has a number that is
related to that in Figure 5. The number is followed by the name (in uppercase letters) written
on the front panel and the type of the element (in lowercase letters). Then, a short description
of the element is given.

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(1) UNFILTERED OUTPUT connector
BNC connector providing an unfiltered voltage proportional to the current passed
through the electrode. The signal is amplified by the GAIN factor selected by switch
(3).
(2) FILT. OUTPUT connector
BNC connector providing a filtered voltage proportional to the current passed through
the electrode. The signal is filtered by a low pass filter and amplified by the GAIN
factor selected by switch (3). The corner frequency of the filter is selected by switch
(5).
(3) GAIN mV/pA switch
6-position rotary switch to set the amplification factor (x0.5, x1, x2.5, x5, x10, x25
mV / pA) of the current proportional voltage signal at (1) and (2).
(4) BOOSTER
Trim pots for adjusting the FREQUENCY BOOSTER.
TIME: Trim pot for adjusting the TIME CONSTANT of the FREQUENCY
BOOSTER.
AMP.: Trim pot for adjusting AMPLITUDE of the FREQUENCY BOOSTER.
Note: The BOOSTER is best adjusted by following the procedure described in chapter 7.2
(5) LOW PASS Hz switch
6-position rotary switch to set the corner frequency of the low pass Bessel filter.
The filtered OUTPUT can be obtained at connector (2).
(6) COMMAND voltage display
LCD that indicates the COMMAND voltage applied to the electrode
(range: 1000 mV, display: XXXX mV). The COMMAND voltage is set
by potentiometer (7).