The Human Computer Trust scale is a psychometric instrument specifically designed to measure human-computer. Both cognitive and affective components of trust are measured; the affective components are the strongest indicators of trust.
instrument has been studied and tested; but no full validation reported yet
– same drawbacks as with all subjective scales
References describing the method
Madsen, M., Gregor, S.: Measuring Human-Computer Trust. In: Gable, G., Viatle, M. (eds.) 11th Australasian Conference on Information Systems, p. 53 (2000)