J2115A Probe Coaxial Isolator
Description
Ground loops exist in many oscilloscope test setups. In particular, the P2104A, P2105A, and commonly available ‘power rail’ probes, which measure small signals, are susceptible to errors caused by ground loops. The J2115A was designed to fit easily into your test setup, inline with your power rail probe, and to virtually eliminate the ground loop connection’s induced errors. A compact footprint, SMA connections, high CMRR, and high bandwidth enable this probe coaxial isolator to significantly reduce ground loop errors in your power rail noise measurements.
Benefits
- Greatly attenuates errors associated with the ground loop in oscilloscope measurements
- Improves the accuracy of power rail probes
- Reduces cable shield-induced ground loop errors regardless of the test setup
- Easy to add multiple J2115A for as many channels as are needed in a test setup
Key Features
- Works with all power rail probes
- Small form factor fits easily into your test setup
- No adjustments necessary
- One male and one female SMA connector, making it easy to insert into your test setup.
- Maintains 50 Ohm transmission line integrity and signal bandwidth to > 2GHz
- Works with all types of test equipment to eliminate ground loops, such as Network Analyzers, Oscilloscopes and Spectrum Analyzers
What’s included
- Two (2) J2115A Probe Coaxial Isolators
- One (1) Year Manufacturer’s Warranty
J2115A Probe Coaxial Isolator
| Characteristic | Rating |
|---|---|
| 3dB Bandwidth | 2.2GHz |
| Insertion Loss 10MHz | 0.1dB |
| CMRR 10kHz | 60dB |
| CMRR 1MHz | 80dB |
| CMRR 10MHz | 80dB |
| GND Saturation Current (50% inductance) | 45mA |
| Ground Resistance | 68mOhm |
| Signal Resistance | 85mOhm |
| Insulation Voltage | > 600V |
| Temperature Range | 0-50°C |
| Maximum Altitude | 6000 Ft |
| Absolute Maximum Voltage | < 50VAC and 75VDC |
| Model | Description | Price |
|---|---|---|
| J2115A | Probe Coaxial Isolator (Qty 2) | Price $650.00 Add to Cart |
Description
The Picotest Probe Coaxial Isolator is a common mode transformer that minimizes the ground loop in power rail and other forms of voltage probe measurements that exist in all oscilloscopes, and other instrument setups.
There is a ground loop created due to the front panel of the instrument and the cable connections at the device under test (DUT). This front panel ground appears across the various scope input channels. Offsets in this ground voltage at the DUT translate to voltage inaccuracies in oscilloscope measurements. The common mode ground signal at the DUT is additive with the desired test signal, and it needs to be diminished and/or effectively eliminated. It can result in mV to tens or even hundreds of mV of measurement offset.
The J2115A Probe Coaxial Isolator is a simple fix for the impacts of the ground loop. The J2115A is essential to achieving the most accurate oscilloscope measurements, especially power rail probe measurements and other voltage probe measurements.
Ground loop errors mostly impact sensitive circuits, such as PLLs or LNAs, but also create VDD droop and ground bounce errors in high power ASIC cores. These ground loops occur when two or more cable shields are connected to “ground” at both ends, with voltage differences between the ground shields at the DUT. There are several papers on the subject (see Application Notes section), but there are a few ways to manage the ground loops:
There are several papers on the subject shown below, but there are a few ways to manage the ground loops:
1 – Reduce the ground connection impedance using low shield resistance cable such as PDN cable
2 – Make at least the most sensitive channel connection as short as possible
3- Add common mode isolators. This is the most effective solution.
Error Note: The ground error is fixed and has nothing to do with the signal amplitude. Representing it as a % isn’t really accurate, but it could easily be hundreds or even thousands of %. The measurement is equal to the ground error plus the signal. These are independent. With no signal, you’ll still see the ground error, indicating an infinite % error.
In this case, you can see the measured differential ground signal (using THDP0200) on CH8. We have a terminated shielded cable on CH5 and the TPR4000 on CH1. Without a ground loop isolator, such as the J2115A, the common mode signal (-30dB) is reduced by only 17dB in the power rail probe and 23dB in the PDN cable, resulting in a significant error.
Inserting the J2115A coaxial isolator improves this from 17dB to 53dB difference for the power rail probe and 60dB for a PDN cable, or more than 100X improvement.
Ground Loops What They Are, Why We Care, and How to Fix Them
Power rail noise is one of the most significant sources of jitter in high-speed systems, phase noise in RF systems, and noise in A/D and D/A converters. Semiconductor manufacturers are responding by continuously improving Power Supply Rejection Ratio (PSRR).
