With Fivedigit Accuracy

The new Type 1151-A Digital Time and Frequency Meter is a more sophisticated brother of the Type 1 lnO-A Digital Frequency Meter previously announced.1 It does not replace the Type 1150-A, but it does extend the range of precision frequency measurement to low frequencies, where a simple counting frequency meter is inefficient. Low frequencies are determined rapidly and accurately by measurement of their periods or decimal multiples of the period. Measurement of higher frequencies is accomplished in the usual fashion, by the counting of zero-crossings per unit time, but an altogether new and highly efficient program is used. Provision is also made for frequency-ratio and multiple-interval measurements in addition to the usual totalizing or accumulative counting functions.

The input circuit includes the controls necessary for measurement of pulsed and low-frequency signals —-trigger level, slope polarity, and ac or dc coupling.

The new counter is available in two versions, the standard model, Type

'!{. W. Frank and .j. K. SkillinK, "A Five-Digit Solid-State Counter for Frequency Measurements to 220 kc," General Radio Experimenter, 36, 4, April, 1962.

1151-A, and the Type 1151-AP* which can be used to drive auxiliary equipment — like the Type 1137-A Data Printer described elsewhere in this issue, f

The other elements of the Type 1151-A counter are similar to the Type 1 loO-A introduced a year ago. Counting decades, quartz-reference oscillator, power supplies, and package are substantially the same.

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