| Electronics > Beginners |
| Question about uni-t 81b mode x1 and x10 with oscilloscope probe HP-3060 |
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| malagas_on_fire:
Hi there. I'm a super fresh new user and this was a post from the review of this particular Meter I've bought once in 2008 an UT81B and worked fine for graphing signals from microcontrollers ( Arduino, Microchip, NXP, etc) and then i sell it cause i stop the electronics and do some stuff on Embedded Linux, becaming a software guy. Now im going back to electronics and i have reorder a brand new uni-t 81B, which i kind like because its handy, simple to use on troubleshooting microcontrolers signals and now Linux SBC's. Its like a old Game Boy in terms of consumption, so i use recharchable batteries and 2000mA gave more or less 10 hours with low brightness ( 3) and contrast around 10. However i don't remember what mode was the proper mode of the oscilloscope probe ( x1 or x10) for direct measuring. In x10 the 1KHz signal generated from a Arduino ( Fast PWM mode) became attenuated with a probe model HP-3060 and the scope does not have option for the x1 and x10 modes... I should have take notes... Dumb me I'll post photos soon |
| malagas_on_fire:
Hi i think i can test the scope with a function generator and maybe get more accurate conclusions, since it has a fixed impedance of 50Ohms. It has been done quite a lot of reviving electronics and solving problems |
| malagas_on_fire:
Before i tested the uni-t 81b and the probe, i was thinking and remembering about the input impedances, more likely the resistor divider created between the input voltage multimeter and the x10 mode probe, using a 5VDC source, it gives almost 1.96V which is near the values of the 8.53MOhm of the probe and the 10M in volt mode. |O The other thing is the added capacitance to the scopemeter voltage input which acts like a integrator for small frequencies ( around 101pF), small signals, but usable for higher frequencies ( above 800Khz). If using mains ( using a isolated transformer ) with x10 it works fine since its out of the band of the capacitve network. So it is direct measure with x1 for small signal , no exceding the Maximum ratings of the probe and hence the scopemeter, and x10 for higher voltages ( example 230V), which matches the specs of this probe . I need to review some of the electronics that i have learn in the past, but today no need for instruments, just using basic stuff reminder. |
| malagas_on_fire:
Here is an example with direct probes and x10 probe with 230V / 117V travel adapter transformer for isolating from mains and using a smaller AC voltage, power. The ratio of the x10 probe plus the input of the scope is about 2.7, since it gave 43VAc rms. So the scope has fixed 10MOhm impedance, the probe is about 6.3Mohm impedance at that voltage / frequency in terms of resistive divider. The same ratio also applies for 230Vac. |
| malagas_on_fire:
I just measured yesterday the DC impedance of the probe and it is 8.53 MOhm, so if we redo the calculations for resistor dividor between probe and scope it would give 14.5 ~14.67MOhm for the impedance of the scope, using the same ratio of 2.7 mentioned above ( 117V / 43V RMS) So the x10 mode is usable for AC mains volts, using a isolation transformer , within the spec of CATII 300V of the probe. The probe itself came with a insulation cap to seal the ground and let a little contact of the tip exposed. I'll post a video of the setup measurement. |
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