| Products > Test Equipment |
| Siglent SDG1000 (aka LeCroy WaveStation) firmware updates |
| << < (6/23) > >> |
| nctnico:
The firmware from Lecroy's website says its version ..2.28 |
| Wuerstchenhund:
--- Quote from: nctnico on April 09, 2013, 11:19:23 pm ---The firmware from Lecroy's website says its version ..2.28 --- End quote --- It seems the LeCroy firmware is always +1 more than the comparable Siglent firmware (odd numbers like the current .27 for Siglent , even numbers like .28 for LeCroy firmware). The next Siglent firmware will probably be .29 or .31, and the next LeCroy version should be .30 or .32. |
| rf-loop:
--- Quote from: commongrounder on April 09, 2013, 10:09:54 pm ---Also, the DB level indication seems way low for the actual output. An actual measured zero dbm (into a high-z input millivolt-meter) level is shown as something like -32dbm on the generator screen. The maximum settable dbm level is -13 on channel 1, and I know the maximum open circuit voltage is 20 volts pk-pk. Am I missing something? --- End quote --- Next, numbers are only "calculated in head" for thinking purpose, not exact values. 0dBm means 1mW! Lets look littlebit. 0.225Vrms to 50ohm is around 1mW power, so we say its level is 0dBm in 50 ohm system. but example 0.225Vrms to 100kohm what is dBm? It is around -32.9dBm For 1Mohm it is -42.9dBm. Also it can not 20Vpp to 50 ohm load. Ok lets take High-Z example 100000k 10Vpp sinewave is roughly 3.5Vrms (rounded) it is -9dBm But for 50ohm load what happend. V drops around half. If there is 1.75Vrms sinewave and load is 50ohm there is around 17.9dBm level. Now I do not know what impedance SDG use for High-Z dBm value calculation. Of course in SDG display value is calculated value from voltage set and impedance. And how this math accuracy. Las time I have used SDG1025 with new FW it show around right dBm for sinewave when also output impedance was set for 50ohm and power was measured with HP power meter (of course 50ohm impedance). I do not remember results but this I remember that result was "acceptable" for cheap instrument. It is good also to note that SDG output is always 50ohm source impedance independent of output setting High-Z or 50ohm. Setting affect only to displayed level setting number. If load is other than High-Z (I do not know what value is High-Z) or 50ohm it need user calculate real level. If you set output to 50ohm (utility menu) then look agen dBm values. Different? "into a high-z input millivolt-meter" and you look what power SDG display. If you use dBm with SDG you need also use 50ohm setting and 50ohm load. Then it show around right. Becouse High-Z... as before. How much it is. If you drive then 1k load or 10k load or 100ohm load. SDG do not know your real load. Number is right if your load is same what SDG use for calculating displayed. (basic things for this read also in User Manual) |
| commongrounder:
Thank you everyone, and especially rf-loop for the excellent discussion. I do understand that dbm refers to measured power into a load. I come from an audio background, so I am used to the reference impedance for dbm as being 600 ohms. My millivolt meter is calibrated to measure 0dbm as .775 volts rms (1mw>600ohms). Personally, I would prefer dbV output levels, which would be independent of loading (i.e. always into "hi-z"), and then be aware of the 50 ohm output impedance to calculate level drops. Most of the gear I work with has a 10k ohm, or higher, input impedance, so there is relatively low circuit loading. The fact is, it is "all in our heads" anyway, and I just need to adjust to how they execute the level setting in the generator. The generator output number one is rated 20 volts pk-pk into an open circuit (so-called "hi-z"). Anyone have thoughts on the log sweep issue? If the Lecroy firmware made a fix to this, I would change over. |
| commongrounder:
Just checked the SDG1005 with my Fluke meter that has dbm with an adjustable reference impedance. With both the meter and the generator set for 50 ohms, into a 50 ohm terminator, the output, as compared to the generator display, is within .01db of right on, so not too bad. In "hi-Z" mode, -30dbm, as displayed on the generator, measures exactly 1 volt rms or 0dbV. I can work with that, since I usually just need to make relative db jumps in level to calibrate equipment. Back to work!!! |
| Navigation |
| Message Index |
| Next page |
| Previous page |