  Using cold 87Rb atoms trapped in a 1D-optical lattice, atomic interferometers
involving coherent superpositions between different Wannier-Stark atomic states
are realized. Two di fferent kinds of trapped interferometer schemes are
presented: a Ramsey-type interferometer sensitive both to clock frequency and
external forces, and a symmetric accordion-type interferometer, sensitive to
external forces only. We evaluate the limits in terms of sensitivity and
accuracy of those schemes and discuss their application as force sensors. As a
first step, we apply these interferometers to the measurement of the Bloch
frequency and the demonstration of a compact gravimeter.
