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Are there major differences in the capabilities of the AN/URM-90(ZM-30/U) and the ZM-3A/U? The 3A is better looking but the 30 has it's own charm and seems to be cheaper. Mainly I would use to test 40s-50s boatanchors.<P>Phil<P>------------------<BR>
I never had much luck making the 90 work properly. What really drove me nuts was that concentric decade switch: it's stiff and there's not enough overtravel on the main dial, so searching for a null can require a lot of switching between ranges. I liked the ZM-11 better. And the GR 1650 better yet. But I use an HP 4260A bridge now. That has indicator lights to tell you which way to go for a balance.<P>I haven't used the ZM-3. As I recall, that works at 60Hz; all the others mentioned run at 1 kHz. The ZM-3 does have a nice leakage test, which the others don't (I use a separate leakage tester that I built myself).<P>------------------<BR>
Phil,<P>The two pieces aren't directly comparable, since they're not the same type of equipment. A ZM-30 (a.k.a. URM-90) is an impedance bridge, but a ZM-3 is a capacitor tester, similar in function and capability to a Sprague TO-6. ZM-3's do use a 1kHz signal in the capacitance test function. <P>Which one might best suit you depends on what type of testing are you looking to do.<P><BR>------------------<BR>
The ZM-3 and ZM-11 are both great cap testers. The ZM-11 has more functions though - the ZM-3 is just a cap tester. A ZM-3 will be bigger, they're built like tanks, and will have all the functions of a TO-6 with two exceptions: ZM-3's don't have a discharge switch (and require moving the cap from function to function) and don't have as low an electrolytic leakage test voltage available as later TO-6's (for cap's that can't take over 50 volts). ZM-11's are much smaller and lighter, but are also very difficult to restore, since much of the internal circuitry can't be accessed without disconnecting wiring. 11's also have a couple trouble spots in their circuitry that will require some work if the one you get has been mistreated. If faced with a choice between two similarly priced, fully functional units, I'd go for the ZM-11. <P>------------------<BR>
Thanks Erik, I like the ZM-3 especially for its looks. I have a cheapo IT-22 now but the mil. units look great with my receivers. <P>-Phil<P>------------------<BR>
Phil,<P>Yeah, the ZM-3 has to be one of the coolest looking pieces of gear ever made. ZM-11's may be smaller, but they're plain vanilla. Mine are hidden, but the ZM-3's are at the front of the shelf. Many factors go into choosing one's gear <IMG SRC="http://antiqueradios.com/forums/smile.g ... -------<BR>
finom1 wrote:I would like to here people think about the (Pyramid Capacitor-Resistor Analyzer CRA-1) and how it compare to the ZM-11 & GR1650 meters.
With respect to the GR 1650-A and GR 1650-B, there is simply no comparison. The General Radio 1650's are lab-grade precision impedance bridges for measuring capacitance, inductance, and resistance. They were not intended to be used for radio repair. They don't have a built-in power supply for biasing electrolytic capacitors, and they do not have a way to measure the leakage current of a capacitor, except indirectly as the dissipation factor.
What the General Radio bridges do offer, that the Pyramid CRA-1 does not, is much higher precision in the measurement of the basic component parameters: capacitance and D, inductance and Q, resistance at DC and at AC.
finom1 wrote:I would like to here people think about the (Pyramid Capacitor-Resistor Analyzer CRA-1) and how it compare to the ZM-11 & GR1650 meters.
With respect to the GR 1650-A and GR 1650-B, there is simply no comparison. The General Radio 1650's are lab-grade precision impedance bridges for measuring capacitance, inductance, and resistance. They were not intended to be used for radio repair. They don't have a built-in power supply for biasing electrolytic capacitors, and they do not have a way to measure the leakage current of a capacitor, except indirectly as the dissipation factor.
What the General Radio bridges do offer, that the Pyramid CRA-1 does not, is much higher precision in the measurement of the basic component parameters: capacitance and D, inductance and Q, resistance at DC and at AC.
Thank you for going into the details of the differences in the meters.
Capacity;
DC leakage current of electrolytic and tantalum caps;
DC leakage resistance of all other kinds of caps;
AC loss (dissipation or dissipation factor, power factor, tan-delta, and ESR) of all caps.
There are no single instruments out there that do all that except for digital bench LCR meters. Be prepared to spend anywhere from $400 to $1,500 for an old, used HP model or perhaps a few hundred dollars for a new Chinese import.
You can get the same functionality out of two or more lower priced instruments used together. Probably the best gadget for the buck on the market right now is the DER-5000 handheld digital LCR meter, which you can buy as an import for about $100 to $140 depending on options. Agilent and B&K have comparable meters which are more costly but at least then you're dealing with US companies for support. Getting the factory test lead set is highly recommended. One of these meters will do everything except the DC leakage current and resistance on capacitors of the sizes commonly used in vintage electronics, and you can also use it for measuring inductors and resistors. Meters like the DER have the same or better accuracy and a couple of other advantages compared to older lab bridges like the GR 1650A; aside from being much smaller and lighter, new, and unlikely to need repairs or recalibration for a long time, they give you a choice of test frequencies and calculate the AC loss in whichever format you prefer.
Then for the DC testing, consider an older model capacitor tester that has a switchable meter for leakage resistance and current. The Sprague TO series testers can do both, and they also make nice backups for "down and dirty" capacitance readings. The TO-6A is the most recent and probably the best in the series because it can be used on the lower voltage electrolytics found in solid state gear, but it is also the most expensive to find today. If you aren't going to get involved in solid state work, a TO-4, -5, or -6 will do just as well and should come in cheaper. A variable voltage DC power supply that covers the working voltages of the capacitors you are using, in conjunction with a milliammeter or microammeter and suitable series resistors, could also be used to measure leakage current and resistance.
The Pyramid CRA-1 is comparable to the earlier TO series capacitor testers and has the ability to measure both leakage resistance and current. But like other older capacitor testers, the bridge voltages may damage the low voltage capacitors used in solid state gear.
"Hell, there are no rules here--we're trying to accomplish something!"
Chris108 wrote:Ideally you want to be able to measure:
Capacity;
DC leakage current of electrolytic and tantalum caps;
DC leakage resistance of all other kinds of caps;
AC loss (dissipation or dissipation factor, power factor, tan-delta, and ESR) of all caps.
There are no single instruments out there that do all that except for digital bench LCR meters. Be prepared to spend anywhere from $400 to $1,500 for an old, used HP model or perhaps a few hundred dollars for a new Chinese import.
You can get the same functionality out of two or more lower priced instruments used together. Probably the best gadget for the buck on the market right now is the DER-5000 handheld digital LCR meter, which you can buy as an import for about $100 to $140 depending on options. Agilent and B&K have comparable meters which are more costly but at least then you're dealing with US companies for support. Getting the factory test lead set is highly recommended. One of these meters will do everything except the DC leakage current and resistance on capacitors of the sizes commonly used in vintage electronics, and you can also use it for measuring inductors and resistors. Meters like the DER have the same or better accuracy and a couple of other advantages compared to older lab bridges like the GR 1650A; aside from being much smaller and lighter, new, and unlikely to need repairs or recalibration for a long time, they give you a choice of test frequencies and calculate the AC loss in whichever format you prefer.
Then for the DC testing, consider an older model capacitor tester that has a switchable meter for leakage resistance and current. The Sprague TO series testers can do both, and they also make nice backups for "down and dirty" capacitance readings. The TO-6A is the most recent and probably the best in the series because it can be used on the lower voltage electrolytics found in solid state gear, but it is also the most expensive to find today. If you aren't going to get involved in solid state work, a TO-4, -5, or -6 will do just as well and should come in cheaper. A variable voltage DC power supply that covers the working voltages of the capacitors you are using, in conjunction with a milliammeter or microammeter and suitable series resistors, could also be used to measure leakage current and resistance.
The Pyramid CRA-1 is comparable to the earlier TO series capacitor testers and has the ability to measure both leakage resistance and current. But like other older capacitor testers, the bridge voltages may damage the low voltage capacitors used in solid state gear.
Chris,
Thank you for all the detail. More then one meter for capacitors is great advice. I will look into the meters that you mentioned.
