A slight correction to a typo in the description below (sorry for the long delay). The correct Tektronix model numbers of these counters start with DC (not TM).
The Tektronix TM500 (manual control) and TM5000 (GPIB or manual control) instruments which used the National Semiconductor MM5837 noise generator chip were the following: DC509 DC510 DC5009 DC5010 These models were manufactured from the early 1980's until 1995. The first two digits of the instrument model number designated the type of instrument. So: DC = Digital Counter DM = Digital Multimeter SG = Signal Generator PG = Pulse Generator AA = Audio Analyzer PS = Power Supply TM = Test Mainframe (which includes the power supply for the plug- in modules) Typically the 10 MHz internal standard or proportional oven timebase (or external 1/5/10 MHz rear edge connector timebase input) is dived down with 7490 TTL /5 and /2 divider sections to 1 MHz. The 1 MHz reference then drives a X100 PLL (using an ECL oscillator with varicap frequency control and 4044 phase detector) to create the 100 MHz main internal clock. The MM5837 pseudo-random noise generator phase modulates the PLL in some instrument modes of operation so that time interval averaging works correctly if the input signal is synchronously related to the clock. -- Bill Byrom N5BB Tektronix Application Engineer On Tue, Jul 19, 2016, at 01:52 AM, Mark Sims wrote: > The Tektronix TM509/5009 (and I think the 5010) counter modules have a > National Semiconductor noise generator chip in them. It injects noise > into the counter to get around counter oscillator/input frequency > synchronization. I was once given a TM509 with a bad noise generator > chip... Some Very Smart People spent ages thinking the > problem was in > the device they were working on until they tried a different counter. > The Very Smart People (too smart to RTFM) could never figure > out why the > counter was flakey and finally tossed it. A little dumpster > diving a few > minutes with a scope yielded a very nice little counter. > > ---------------------------- >> Universal timer/counters and equivalent time sampling DSOs can have > this problem when their timebase ends up synchronized with the signal > they are measuring. > _________________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
