Additional in-situ measurements during piezocone penetration tests can provide important information at a low cost due to recent advances in measurement technology. Resistivity measurements, commonly used in geophysical measurements, can be adapted to a standard piezocone penetration test (CPTU) to supply data about the in-situ properties of the soil. Change in soil density in extensive sand layers can therefore be determined. A series of laboratory multi-frequency AC resistivity tests with a novel electrode configuration have been performed with a model probe to investigate possibilities of in-situ measurement of volumetric properties of sand in a controlled saturated sand sample. The results show that soil density change of saturated sand can be measured efficiently and with relative accuracy with resistivity measurements at multiple frequencies. A measurement frequency spectrum of 100 Hz to 100 kHz is recommended for in-situ tests.