HELP:Low-pass filter on frequency counter

[caius]

Hi all,
I have to made some measurements with a frequency counter (model VC3165) on
low frequencies (up to 60 Hz) .I know that in case of low frequency
measurements a low-pass filter is needed in order to obtain stable and
precise readings.
My frequency counter has only an AC/DC button (to be used with a low-pass
filter as said in the service manual) but it doesn't have an integrated
low-pass filter (many counters have it).

I built some simple RC filter ( using a resisitor and a capacitor) with
various cut-off frequncy ( I tried 15 Khz and 50 Khz) but I alway obtain
floating and not precise readings on low frequencies.
How can I solve this problem?Maybe using a low-pass filter like these(very
expensive IMHO)?:

http://cgi.ebay.com/AGILENT-HP-10856A-LOW-PASS-FILTER-KIT-5KHz-50KHz-500KHz-/120668081898?pt=LH_DefaultDomain_0&hash=item1c1860ceea

or building a proper one (but as said before simple RC filters didn't work)?

 

[JeffM]

caius wrote:

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