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Operation
3
GENERAL INFORMATION
DYNAMIC RANGE
DA1855A-OM-E Rev A
The DA1855A has been designed to be used with oscilloscopes
equipped with a ProBus interface. Connecting the Differential
Amplifier to the oscilloscope through the ProBus interface will
automatically control all the required settings from the
oscilloscope and will lock-out the DA1855A front panel controls.
All front panel controls are now accessible through the
oscilloscope user interface. The DA1855A user interface can be
viewed by pressing the Coupling button when the channel
connected to the DA1855A is selected. The DA1855A front panel
controls will operate manually when the Differential Amplifier is
connected to an oscilloscope not provided with a ProBus
interface.
Removing the ProBus interface cable with the differential
amplifier still powered up, requires the DA1855A to be
turned OFF and ON to access the front panel controls.
The basic amplifier dynamic range in X1 Gain and 1 Attenuation
is ± 0.500 V. Changing the gain and or attenuation will affect both
the Differential Mode and Common Mode ranges.
The Differential Mode range is scaled by both gain and attenua-
tion, while the Common Mode range is scaled by attenuation
only. Refer to table 3-1.
Table 3-1. Dynamic Range
Gain
Atten*
1
1
1
10
10
1
10
10
* Attenuation, Common Mode and Differential Mode ranges are
scaled with external probe attenuation. A 10 probe will increase
all these values by a factor of 10.
ISSUED: July 2002
Note:
Differential Mode*
Common Mode*
± 0.5 V
± 5.0 V
± 50 mV
± 0.5 V
Operation
± 15.5 V
± 155 V
± 15.5 V
± 155 V
3-1
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Related Manuals for LeCroy DA1855A
Summary of Contents for LeCroy DA1855A
-
Page 1: General Information
Operation Operation GENERAL INFORMATION The DA1855A has been designed to be used with oscilloscopes equipped with a ProBus interface. Connecting the Differential Amplifier to the oscilloscope through the ProBus interface will automatically control all the required settings from the oscilloscope and will lock-out the DA1855A front panel controls. -
Page 2: Front Panel
Input Connectors Signals applied to the +INPUT and the –INPUT are connected either directly to the DA1855A amplifier’s inputs or to the input attenuators. Maximum input voltage is ±200 Vp A signal connected to the +INPUT will remain its polarity at the output connector. - Page 3 Precharge is particularly useful prior to selecting AC coupling when the input voltage has a DC component in excess of 19 V. The DA1855A input coupling is set to OFF and connected to the circuit under test. When the...
- Page 4 V (comparison voltage). COMP The DA1855A contains a precision DC voltage source which is controlled by the oscilloscope OFFSET control. (When the amplifier is used stand alone, without ProBus interface to a LeCroy oscilloscope, the voltage is controlled by the push buttons above and below the front panel numerical display.) This voltage...
- Page 5 Operation The DA1855A's amplifier subtracts the voltage applied to its inverting input from the voltage applied to its non-inverting input. The DA1855A output is therefore zero whenever these two voltages are equal. For this reason, the voltage applied to the inverting input is called a comparison voltage, V .
- Page 6 The increase in common mode voltage range also applies when using attenuating probes. When the DA1855A is used with attenuating probes that feature readout, the PVG display is changed to indicate the voltage at the +INPUT probe tip which will bring the amplifier output to zero.
- Page 7 PVG to DIFF inject a calibrated offset signal into the DA1855A while still using both inputs for full differential operation. This mode can be used as a position control to move the trace on the oscilloscope screen in preference to using the oscilloscope's position or offset control.
- Page 8 Effective Gain Six indicators (LEDs) across the top of the DA1855A front panel show the total gain from the instrument input to output. Logic within the amplifier includes the gain, internal attenuation, and probe attenuation factors (when readout encoded probes are used) to determine the effective gain.
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Page 9: Rear Panel
Transient and frequency response are independent of the load impedance. Overload When a signal, which could damage the DA1855A, has been applied to either input connector, the DA1855A protects itself by disconnecting the signal. The input coupling mode changes to OFF, and the OVERLOAD light is turned on. - Page 10 Power up indication Upon turn-on, the model number and firmware version are briefly displayed in the PVG readout. For example, 1855.12 indicates that the instrument is a model DA1855A and the firmware version is 1.2. Precision Voltage Generator Offset Voltage The rear panel OFFSET VOLTAGE BNC (PVG) output connector, is a monitor of the Precision Voltage Generator (PVG).
- Page 11 Effective voltage is always referred to the input of the DA1855A or the probe tip if a probe is used. When using probes, the maximum effective voltage range may be limited by the maximum voltage rating of the probe.
- Page 12 50 Remote Operation A REMOTE connector on the rear panel of the DA1855A allows total control of the instrument through a LeCroy oscilloscope when connected to ProBus using the supplied cable. All of the instrument functions can be controlled through the oscilloscope user interface.
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Page 13: Instrument Settings
Remote operation requires software version V8.1.0 or higher. Probe Coding Input This jack is to be used with LeCroy DXC series probes to detect the probe attenuation factor. Other manufacturer’s probes with standard probe coding capability will be properly decoded through the DA1855A's front panel +INPUT BNC connector. - Page 14 “DC”. Subsequently adjust the trace position on the oscilloscope screen using the DA1855A PVG and mode or V input. This assures that the oscillo- DIFF COMP scope is set to the center of the DA1855A's dynamic range. 3-14 ISSUED: July 2002 DA1855A-OM-E Rev A...
- Page 15 100µV/div and the DA1855A in the X10 GAIN mode, the overall scale factor will be 10µV/div. In the X10 GAIN mode, the DA1855A has lower noise than many oscilloscopes, so it is preferable to use the /DA1855A X10 GAIN mode and a lower oscilloscope scale factor. For example, to...
- Page 16 When set to Manual mode, the dynamic range of the VOLTS/DIV knob is limited to the scale factors which can be obtained without changing the DA1855A gain or attenuation. Thus in Manual gain control mode, only the scale factor of the oscilloscope will be changed.
- Page 17 ÷10 and ÷100 attenuating probes also extend the common mode range of the differential amplifier. For example, the DA1855A amplifiers have a common mode range of ±15.5 volts when their internal attenuators are set to ÷1 and 155 volts when set to ÷10. The addition of a probe with an attenuation factor of ten will extend the common mode range to 1550 volts or the rating of the probe, whichever is less.
- Page 18 The DXC100A Differential Probe Pair The DXC100A is a high performance matched passive differential probe pair designed for use with LeCroy DA1855A series differential amplifiers. The probe pair consists of two well- matched individual probes that share a common compensation box to allow the attenuation factor on both probes to be simultaneously switched between ÷10 and ÷100.