Operator’s M anual TF-DSQ Probe Calibration and Deskew Fixture
TF-DSQ Probe Calibration and Deskew Fixture Operator's Manual July, 2009
LeCroy Corporation 700 Chestnut Ridge Road Chestnut Ridge, NY, 10977-6499 Tel: (845) 578-6020, Fax: (845) 578 5985 Warranty LeCroy warrants this oscilloscope accessory for normal use and operation within specification for a period of one year from the date of shipment. Spare parts, replacement parts and repairs are warranted for 90 days.
Operator's Manual TABLE OF CONTENTS TF-DSQ Overview .................................................................................... 6 Probe Calibration with the TF-DSQ Fixture.............................................. 6 Probe Calibration Steps with the TF-DSQ Fixture .................................... 7 TF-DSQ Connections ................................................................................ 8 TF-DSQ Fixture Overview ......................................................................
TF-DSQ Probe Calibration and Deskew Fixture Safety Precautions ................................................................................ 28 CERTIFICATIONS .................................................................................... 28 CE Declaration of Conformity ................................................................ 28 EMC Directive ........................................................................................ 28 Electromagnetic Emissions: ................................
Operator's Manual TF-DSQ Overview Probe Calibration with the TF-DSQ Fixture The TF-DSQ fixture is used in conjunction with the oscilloscope software to perform probe deskew and DC calibration.
TF-DSQ Probe Calibration and Deskew Fixture Probe Calibration Steps with the TF-DSQ Fixture Probe calibration is accomplished with the TF-DSQ fixture by following the steps in the following flowchart. Note: It is recommended that you read the instructions presented here in their entirety to familiarize yourself with the advanced features of the TF-DSQ fixture prior to use. The combination of TF-DSQ fixture and oscilloscope software is designed with an important use model.
Operator's Manual TF-DSQ Connections TF-DSQ Fixture Overview The TF-DSQ fixture comes in a soft case containing a CD with .
TF-DSQ Probe Calibration and Deskew Fixture A ProLink extender A BNC to SMA adapter (not pictured) TF-DSQ Fixture Elements TF-DSQ-OM-E RevC 9
Operator's Manual Assembling the TF-DSQ fixture See the fixture overview to identify individual components. System assembly is accomplished in the following steps: 1. Connect one end of the 50 Ω cable to the desired ProLink or ProBus extender (with adapter). 2. Connect the other end of the 50 Ω cable to the SMA connector on the TF-DSQ fixture. 3. Connect the ProLink or ProBus CAT 5 cable from the extender to the TF-DSQ fixture.
TF-DSQ Probe Calibration and Deskew Fixture TF-DSQ Oscilloscope Connection The TF-DSQ fixture is connected to either an unused oscilloscope channel or the external AUX IN input, if one exists. In other words, any oscilloscope channel or oscilloscope input with a ProLink or ProBus connector.
Operator's Manual Probe Connection to TF-DSQ The TF-DSQ provides multiple probe connectors for various kinds of probes. Probes are connected electrically in either a single-ended or differential arrangement, depending on the type of probe. Probes are connected mechanically using either the probing pads, or a probing clip provided for solder-in probing solutions. Figure 4-1.
TF-DSQ Probe Calibration and Deskew Fixture Figure 4-3. Differential Probe Properly Connected to the Fixture (Browsing Configuration) Figure 4-4.
Operator's Manual Probe Calibration Probe Calibration Menu Accessing the Probe Calibration Menu The probe calibration menu can be accessed from the Vertical drop-down menu or from the Channel (sometimes referred to as Vertical Adjust) dialog: Probe Calibration Menu Description Figure 4-5. The Probe Calibration dialog contains information and controls.
TF-DSQ Probe Calibration and Deskew Fixture Note: The Cal Skew Ref field (and others) shows EXT for External Trigger Input. This may also be more aptly referred to as AUX for Auxiliary Input. This Probe Calibration dialog field could also be a channel. PROBE CHANNEL AND TYPE IDENTIFICATION This area shows the type of probe connected to the channel. All other information shown in a given row is associated with that probe.
Operator's Manual PROBE DESKEW INFORMATION The probe deskew information contains the measured skew between the probe in the specified channel and the reference channel. It can be entered manually or as the result of an automatic calibration. In the case of automatic calibration, it can be the result of a portion of the full calibration-1427781181 or it can be the result of a standalone deskew calibration. Even after the deskew has been performed automatically, the deskew correction can be tweaked manually.
TF-DSQ Probe Calibration and Deskew Fixture Basic Probe Calibration The TF-DSQ fixture is used to calibrate probes. Prior to beginning your measurements: 1. Assemble the TF-DSQ fixture 2. Attach the fixture, ideally to the Auxiliary Input or an unused oscilloscope channel 3. Access the Probe Calibration Menu Now, follow these steps for each probe used: 1. 2. 3. 4.
Operator's Manual Deskew Only Pressing this button performs only the deskew calibration of the probe on the specified channel. See details Probe Deskew Calibration. The Advanced Menu The Advanced Menu contains information and functionality useful to the advanced user of the TF-DSQ fixture.
TF-DSQ Probe Calibration and Deskew Fixture Common Mode Voltage Selection The TF-DSQ fixture calibrates probes differentially or in single-ended mode depending on the type of probe. Differential probes allow the common mode voltage component to be applied during the DC calibration for improved calibration accuracy in situations where probe gain or offset correction depends on common mode components. See Probe DC Calibration or Differential and Single-ended Probe Basics for details.
Operator's Manual Two channels are properly deskewed relative to each other when the difference between the deskew values entered for each channel aligns an edge occurring at the same time and applied to both channels. A channel is properly deskewed in an absolute sense when an edge is applied to that channel, the oscilloscope is triggered on that edge, and that edge appears such that the trigger threshold crossing appears at the trigger delay, which is the zero time reference on the oscilloscope screen.
TF-DSQ Probe Calibration and Deskew Fixture The following example illustrates this scenario: Two probes are used in a system. They are connected to channels 2 and 3. The TF-DSQ fixture is connected to channel 4. When the oscilloscope is triggered on channel 4, you observe the following edges: When the probes are deskewed, the relative time between channel 4 (where the TF-DSQ fixture is connected) and channel 2 is calculated as 30 ps, and -30 ps and is entered in channel two's skew entry.
Operator's Manual Deskew Risetime Adjustment Theory Two scenarios require adjustment of the deskew values to account for risetime: 1. Two probes are used for relative time measurements, but each probe has a different risetime. 2. Two probes are used for relative time measurements, but each signal has a different risetime. The first case is explained here with obvious analogy to the second case. Two probes are often utilized for measurements where each probe has a different risetime.
TF-DSQ Probe Calibration and Deskew Fixture Now, let's assume that these probes are applied to signals with the same risetime, but a different risetime than the one applied by the deskew fixture: This example clearly illustrates how the application of signals with the same risetime (but different risetime than the one applied by the deskew fixture) produces a deskew error, unless compensated.
Operator's Manual The TF-DSQ fixture, in accordance with the philosophy of requiring only one calibration in the fixture, handles this in a special manner. The user simply enters the measured risetime of the signals after the probe is connected to the circuit. Since the oscilloscope software saves the edge acquired during the deskew calibration process, it applies this saved edge to a variable filter using digital signal processing until the measured risetime is achieved.
TF-DSQ Probe Calibration and Deskew Fixture The gain and offset correction applied during DC calibration affects the voltage measured according to the following formula: where V is the voltage measured prior to calibration. Probes are calibrated for each fixed gain setting of the oscilloscope, meaning they are calibrated at 10, 20, 50, 100, 200, 500 mV and 1V per division. A unique gain and offset calculation is made for each range. The calibration of the probe is performed utilizing 5 DC levels.
Operator's Manual In this case, the outer conductor connects the oscilloscope's ground to the circuit's ground, and the cable is terminated with 50 ohms at the oscilloscope, such that the conductor looks like 50 ohms looking into it at all frequencies. In the case of single-ended measurements, the oscilloscope is measuring the difference between the probe tip and ground. Since ground is considered to be zero volts, one can say that the voltage measured at the probe tip is the absolute voltage.
TF-DSQ Probe Calibration and Deskew Fixture Despite differential probes measuring differentially, they can be used to measure common mode signals. In this case, the V- tip is connected to ground, and the probe continues to measure the difference between the tips. This is a useful configuration for identifying ground problems.
Operator's Manual Operating Environment Before using your accessory, ensure that its operating environment will be maintained within these parameters: Temperature: 5 to 40 °C. Humidity: ≤ 80% RH (non-condensing). Altitude: 2000 meters Max. Safety Precautions CAUTION Avoid personal injury or damage to your accessory or any equipment connected to it by reviewing and complying with the following safety precautions: Use only as intended.
TF-DSQ Probe Calibration and Deskew Fixture Electromagnetic Emissions: EN 55011/A2:2002, Radiated and conducted emissions (Class A)* Electromagnetic Immunity: EN 61000-4-2:2001 Electrostatic Discharge. (4 kV contact, 8 kV air, 4 kV vertical/horizontal coupling planes) EN 61000-4-3:2006 RF Radiated Electromagnetic Field. (3 V/m, 80-1000 MHz; 3 V/m, 1400 MHz - 2 GHz; 1 V/m, 2 GHz - 2.7 GHz) * This is a Class A product.
Operator's Manual Index deskew risetime adjustment, 21 C differential & single-ended probes, 24 gain & offset, 23 calibration: probe, 13 high-speed edge, 21 P probe calibration, 13 overview, 7 probe calibration menu, 13 probe connection, 11 probe DC information, 14 T TF-DSQ, 5 probe deskew information, 15 recall calibration, 15 absolute skew, 19 relative skew, 19 advanced probe calibration, 18 rise time skew correction, 17 assembly, 9 scope connection, 10 basic probe calibration, 16 skew ref
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