2. Avoiding Expensive Repairs!
You were all excited about your new oscilloscope, you connected a signal to a front-panel input, and immediately destroyed an input channel. Truly a bad and avoidable day! Always handle the oscilloscope (and any high-performance instrument) armed with the knowledge stated in the following caution and covered in Safety Essentials 2 through 7:
Design constraints required to perform today's high performance measurements result in electrical inputs that are more vulnerable to damage caused by Electrostatic Discharge (ESD), overvoltage, and transients. In addition, the required small physical geometry of high frequency connectors, adapters, cables, limiters, pickoffs, and other devices and instruments results in hardware that is easily damaged by improper torque. In the case of 1 mm connectors, even finger tightening can cause permanent damage! Read the information in Safety Essentials 5 to learn how to protect your oscilloscope from improper torque techniques.
Observe Front-Panel Labels
On N1000A and 86100D DCA-X oscilloscopes and oscilloscope and clock recovery DCA-Ms, the front and rear-panel input connectors are labeled with the maximum allowable signal levels before damage.
Use Limiters to Protect against Transients
The Keysight N9355CK01 is a DC coupled limiter (DC to 26.5 GHz) that is used to protect sensitive oscilloscope channels from damage due to electric overload stress (EOS) and electrostatic discharge (ESD). For example, voltages in excess of ±2V can damage high-performance samplers used in oscilloscopes. The limiter dramatically reduces the likelihood that such voltages will reach the sensitive part of the instrument, ensuring that the oscilloscope will perform reliably. Instruments with dual electrical channels, such as the 54754A, will require two N9355CK01 limiters. Step generators within the TDR modules use
≤0.2V, which is less than the diode threshold of the N9355CK01 limiter. The N9355CK01 can also be used to protect the electrical channel of the 86105x and similar modules, as long as the signal does not exceed –0.5V to +0.5V. The N9355CK01's voltage drop is ±0.6V to 0.7V at ±10 mADC.
The N9355CK01 will protect instruments from occasional and short voltage spikes. A major power source, such as a high voltage and current supply can still cause severe damage to the limiter itself, or the instruments. Operators should continue using industry standard EOS and ESD practices to minimize this risk.
Figure. Two N9355CK01s Inserted into Signal Paths
Always confirm that the output of any Device Under Test (DUT) does not have any transient voltages that can damage the oscilloscope's input circuits. Place a limiter on the oscilloscope's input if transients are a possibility.
Use Connector Savers
Connector savers are useful in prolonging instrument life and ensuring better quality measurements. Refer to the following table for a list of commonly used connector savers.
| Connector | Comments | Part Number |
|---|---|---|
| 7 mm | Not available | |
| Type-N 50 ohm | Not available | |
| Type-N 75 ohm | Instrument grade | 85036-60015 |
| 3.5 mm | Metrology grade | 85052-60013 |
| 3.5 mm | Instrument grade | 85059C |
| 2.92 mm | 2.4 to 2.92 adapters | 11904 |
| 2.4 mm | Metrology grade | 85056-60007 |
| 1.85 mm | Instrument grade | 85058-60009 |
| 1.0 mm | Not available |