KeepItSimpleStupid
- Joined Mar 4, 2014
- 5,088
Isolation: If you do use an isolation transformer, you don;t want isolation in the true sense.
You want N (to instruments) and G (to instruments) of the secondary to be bonded together, and to the incoming ground.
There's shielded line cords. I only used a shielded line cord when driving heaters in an RF (13.56 MHz) chamber. The controllers had RFI filters fitted on the incoming power. I designed it this way so I didn;t have to "fix" anything.
I won't say that a shielded power cord would help.
I used 2 ohms as an estimate. 0.5 resistor + 1.5 ohms for the wires and definitely less than 100 mA.
You definitely have to increase the compliance voltage. The power supply can;t make up it's mind between constant current and constant voltage.
Small resistors are sometimes use to isolate capacitive loads. Your problem is that your current limiting can be competing with your required 100 mA. Your resistor may have a 1% tolerance, so it could already be 50.5 ohms. You can't deliver 100 mA into 50.5 ohms and at 5 volts. The 5 Volts wins. I<100 mA.
1. The voltage across a capacitor cannot change instantaneously
2. The current in an inductor cannot change instantaneously.
3. Everything has parasitics.
You want N (to instruments) and G (to instruments) of the secondary to be bonded together, and to the incoming ground.
There's shielded line cords. I only used a shielded line cord when driving heaters in an RF (13.56 MHz) chamber. The controllers had RFI filters fitted on the incoming power. I designed it this way so I didn;t have to "fix" anything.
I won't say that a shielded power cord would help.
You have a 1% resistor. It could be high by 1/2 an ohm. If it is, you can't deliver 100 mA by definition.Could I use a smaller resistor to reduce the noise and still get a definitive spike during discontinuity?
I used 2 ohms as an estimate. 0.5 resistor + 1.5 ohms for the wires and definitely less than 100 mA.
You definitely have to increase the compliance voltage. The power supply can;t make up it's mind between constant current and constant voltage.
Small resistors are sometimes use to isolate capacitive loads. Your problem is that your current limiting can be competing with your required 100 mA. Your resistor may have a 1% tolerance, so it could already be 50.5 ohms. You can't deliver 100 mA into 50.5 ohms and at 5 volts. The 5 Volts wins. I<100 mA.
Remember two axioms:Does the Transient response of the power supply not matter when the resistor is being used?
1. The voltage across a capacitor cannot change instantaneously
2. The current in an inductor cannot change instantaneously.
3. Everything has parasitics.
The lower the value of the resistance, the lower the noise, so I don;t think 50 ohms is significant.[/QUOTE]Would the noise in the resistor Im seeing be a case of Johnson-Nyquist Noise?