Don't get overly concerned about accuracy, meters are not accurate, they only get you in the ball park so to speak, or they show you that 'something' is in the water besides water. TDS meters will indicate the dissolved or ion content but won't show you particle content, and you'll have both ions AND particles present, so TDS meters will only give you *some* information, laser pointers will indicate you have *some* particle content. TDS meters are basically electrical conductivity meters measuring the dissolved content and estimates the ppm, I repeat...estimate! A basic stock standard TDS meter requires the reading to be roughly doubled to get a better estimate of ppm, again I repeat...estimate! But they will be close enough for your 'in house' purposes.
If you desire absolute accuracy you'll have to have some laboratory analysed.
You don't need to be that accurate in the scheme of things silver related.