A Digital Integrator with a Memory

An inexpensive (∼ $120), versatile, easily constructed digital integrator is described. Linearity is better than 1% for voltages of 0.1 to 15 V inputs. Input uncertainties are ≤ ∼ 200 μ V. Input impedance is ∼ 0.5 M. Integrals spanning at least a 1000:1 range can be read with 1% or better accuracy without varying the gain. Sensitivity is 5 count/V-sec, but higher or lower sensitivities are available by changing component values. A memory permits the integral at a particular instant to be locked into the display without any effect on the continuing integration. The reset, store, and track controls are transistor transistor logic compatible and may be operated by external circuitry for added versatility.